Phialopecten triphooki (Zittel, 1865)
ZITTEL, K. A. 1865. Fossile Mollusken und Echinodermen aus Neu-Seeland. In F. von Hochstetter, M. Hörnes & F.R. von Hauer (Eds.), Paläontologie von Neu-Seeland. Reise der Österreichischen Fregatte Novara, Geologischer Theil, 1 (2): 15-68, pls. 6-15. [p. 52, pl. 11, fig. 4]
K. A. Zittel, 1865, plate 11.
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«Char. Testa solida , rotundata, compressa costis elevatis viginti ornata. Costae crassae, obsoletae, annulatae, interstitiis aequalibus uniradiatis transversim striatis. Auriculae magnae striatae.
Höhe ungefähr 80 Millim., Länge 70 Millim. Das nur unvollständige Stück dieser grossen Species weist auf eine länglich-runde Form der Schale hin. Die Oberfläche ist mit etwa 20 dicken kräftigen Radialrippen versehen, die durch stumpfe, dachziegelartige, sehr wenig erhabene Schuppen eine rauhe Oberfläche besitzen. Die etwa gleichbreiten Zwischenfurchen sind quergestreift und gewöhnlich von einer schwachen Radialrippe durchzogen. Die Buckeln bilden einen wenig stumpfen Winkel und die ziemlich starken, durch eine tiefe Furche getrennten Ohrflügel sind mit ungleichen Eippen bedeckt, von denen die unten stehenden die schwächsten sind. Die Ähnlichkeit dieser Art mit dem jetzt lebenden P. crassicostatus Reeve, dessen Vaterland unbekannt ist, ist ziemlich gross, sie unterscheidet sich von demselben nur durch die Verschiedenartigkeit der Ohren, so wie durch die auf den Seiten mit Schuppen versehenen Rippen. Pecten rudis (Sow. in Darw. Geol. Obs. S. Am. p. 25-i. PI. in. f. 32) aus Chiloe ist ebenfalls eine sehr nahestehende Form. Name nach Herrn Triphook in Ahuriri. Vorkommen: In kalkigem Conglomerate an der Hawkes-Bay, Nordinsel.» KARL ALFRED VON ZITTEL, 1865
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«Type material. Pecten triphooki holotype NHMW 1959/335/43, from locality 6, Napier; excellent modern plaster replica GNS TM2712. Named after Thomas Dawson Triphook, a surveyor in Napier, who presented fossils to Hochstetter (Zittel 1865, p. 52). Fleming & Hornibrook (in Flügel 1959) designated Milton Road, Napier, in Scinde Island Limestone (early Nukumaruan, early Pleistocene; Beu 1995, p. 137) as the restricted type locality, based on information from T.L. Grant-Taylor. Pecten accrementus, lectotype GNS TM2817, from Scinde Island Limestone, Napier; an aberrant specimen.
Dimensions. Holotype of Pecten triphooki: H 61, L 64 mm (including partial mould of shell interior); illustrated specimen, GNS TM5441, GS576, V21/f8470, Scinde Island Limestone (early Nukumaruan, early Pleistocene), Milton Road, Napier: H 110.9, L 115.6 mm.
Remarks. The locality and the illustration by Zittel (1865, pl. 11, fig. 4) leave no doubt that P. triphooki refers to the youngest species of the Phialopecten lineage, limited to a brief zone in early Nukumaruan (early Pleistocene) rocks, and the identity of this species is well known (Beu 1995, p. 42, figs 18b, 19a-d, 20a-d). The holotype is not illustrated again here as it reveals few of the diagnostic characters of adult Phialopecten triphooki, but a good topotype is illustrated for comparison (Fig. 13G). This species reaches at least 135 mm in height, and the holotype is a small fragment. It is an incomplete, moderately inflated right valve, bearing obvious commarginal ridgelets between the radial costae, one secondary radial costa between most (but not all) pairs of primary costae, and a weak median groove along the crests of a few of the costae on the posterior part of the disc. The specimen is not large enough to reveal the regular, prominent central grooves on costal crests that characterise the outer half of the disc of P. triphooki (Beu 1995), but there is no doubting its identity or its matrix of Scinde Island Limestone.»
BEU, A. G., S. NOLDEN & T. A. DARRAGH. 2012. Revision of New Zealand Cenozoic fossil Mollusca described by Zittel (1865) based on Hochstetter’s collections from the Novara Expedition. Memoirs of the Association of Australasian Palaeontologists, 43: 1-69, figs. 1-21. [p. 35, 37]
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Phialopecten triphooki (Zittel, 1865); A. G. Beu, S. Nolden & T. A. Darragh, 2012, Revision of New Zealand Cenozoic fossil Mollusca described by Zittel (1865) based on Hochstetter’s collections from the Novara Expedition, figure 13G.
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«REMARKS: Phialopecten triphooki is restricted here to the basal Nukumaruan terminal species of the Phialopecten lineage. P. triphooki differs from its presumed immediate ancestor, P. thomsoni, in its smaller size (both mean and maximum), in having slightly more numerous radial costae (the frequency peaks at 24 rather than 21 costae in eastem North Island populations), in having more nearly equal inflation of the two valves (left valve more markedly inflated than right in P. thomsoni), in having costae of more nearly even width on the two valves (indistinguishable in many specimens, compared with low, wide, closely spaced RV costae and high, narrow, widely spaced LV costae in P. thomsoni), in having costal crest sculpture dominated by a median deep groove, rather than evenly and regularly subdivided on the right valve into 4-6 riblets as in P. thomsoni, and in having the auricles divided from the disc by deeper and more obvious grooves in most specimens (but not in the Oope Road form). In Hawke's Bay populations, the huge, triangular auricles of P. thomsoni distinguish it from the smaller and more nearly square ears of P. triphooki, but this does not hold in Wanganui basin, suggesting that ear shape varies phenotypically in P. thomsoni.
Forms of Phialopecten triphooki: An aspect of this whole project that has proved to be fundamental is the recognition of several ecomorphs of Phialopecten triphooki. The recognition that these are ecophenotypic forms rather than having an altemative explanation (distinct species; genetically separated geographic subspecies; succeeding species resulting from continued evolution through early Nukumaruan time) came from field collecting from Otope Limestone at its type locality, a small side-valley off Otope Road, between Kumeroa and Dannevirke, and is described more firlly below under Otope Limestone. As the two most common forms are common and widespread, are referred to under several early Nukumaruan formations, and are critical to the tectonic reconstruction, they deserve separate discussion here. (a) P. triphooki (sensu stricto) (Fig. 19a-d): the type locality of P. triphooki was designated by Fleming & Hornibrook (in Flügel t959, p.843) as Scinde Island Limestone at Milton Road, Napier (grid ref. N134/323000; metric grid V21/460843). They realised, following the then-unpublished work of Kingma (1971), that this limestone is of early Nukumaruan age. The name therefore applies srictly to specimens from Scinde Island Limestone at Napier and to closely similar specimens. Diagnostic characters are the relatively wide, low main costae with a prominent wide median groove on the crest, and several more minor riblets and grooves on either side of the median groove, and relatively small, thick and solid, coarsely radially costate auricles separated from the disc by a deep, obvious groove. Two valves, purportedly from Napier, in early collections (a wide-ribbed, complexly subdivided right valve, and a narrowly ribbed, highly inflated left valve) appear to belong in P. thomsoni and have a cream (rather than white to pale gey) matrix, and so appear likely to originate from Te Onepu Limestone (Mangapanian); the reliability of the provenance of early collections should be reated with caution. Specimens agreeing with typical Napier shells in diagnostic characters are listed, under P. triphooki sensu stricto, in Appendix A; they are known only from early Nukumaruan Te Aute lithofacies: Scinde Island Limestone along the southeast side of Mason Ridge, on Te Onepu Road and in the valley above Mahana Station, Anaroa Road, Raukawa; Pakipaki Limestone in both the former Pakipaki quarry on Anderson Road and the more recently operated quarry on fhe hilltop to the south; Waitahora Limesone in Waiahora Valley, northwest of the northern Puketoi Range, southeast of Dannevirke; the uppermost, Te Aute facies member of Oope Limestone at Otope Road; and a small proportion of specimens from Whanawhana Limestone on the southernmost Glenross Range, north of Big Hill and the Ngaruroro River in western central Hawke's Bay (most specimens observed in the uppermost shellbed member of Whanawhana Limestone are the following form). (b) P. "narrow-ribbed triphooki" (Fig. 18b,20a,c,d): distinctive characters are the consistently high, narrow, closely spaced radial costae, in most cases with only a weak median groove and little other sculpture on costal crests. As most specimens are from highly cemented limestone (as formerly abundant aragonitic shells in the matix have yielded calcite to cement the rock at most localities) few have well preserved auricles; those few known are much like those of typical Napier specimens. At Otope Road, north of Kumeroa, P. "narrow-ribbed triphooki" is limited to uncemented aragonitic shellbeds in brown-weathering sandstone forming the central member of Oope Limestone, and this gives the clue to the distribution of this narrowly costate form: it occurs only in eady Nukumanran aragonitic bivalve-dominated shellbeds, and their diagenetically altered equivalents. Specimens are known from parts of Whanawhana Limestone on the southernmost Glenross Range; from Otope Limestone in blocks in the depression east of Groome Road, Takapau, and at several localities between Kumeroa and Dannevirke, west of the Waewaepa Range; in Ngaruru Limestone at Mikimiki, nofhwest of Masterton; and in Nukumaruan Pori Limesone (as redefined below) between Coonoor and Makuri, west of the Pukeoi Range. (c) P. triphooki "Otope Road form" (Fig. 20b): distinctive characters are its small size, its thin shell, is very low, wide radial costae, and its unusually thin, weakly sculptured auricles separated from the disc by much shallower, narrower grooves than in either P. tiphooki sensu stricto or P. "narrow-ribbed triphooki". Subdivision of costal crests is relatively fine and weak; most specimens have three low, narrow riblets on left valve costae and four on right valve costae. The Oope Road form therefore resembles P. thomsoni much more nearly than any other form of P. triphooki does. At Otope Road, between Kumeroa and Dannevirke, P. triphooki "Otope Road form" occurs commonly in the cemented shelly mudsone forming the uppermost member of Otope Limestone. However, it is limited to this lithology, and is not known definitely from any other locality. A large, low-ribbed, poorly preserved specimen from Otope Limestone at Totara Road, Kumeroa (GS8648,T24/f7607, T24/673896), referred tentatively to P. thomsoni, is possibly a very large specimen of P. triphooki "Otope Road form". (d) P. triphooki "Hautawa form": specimens of Phialopecten triphooki from Hautawa Shellbed, between Hunterville and the Turakina Valley in Wanganui basin, closely resemble P. "narrow-ribbed triphooki" in most characters, particularly in rib profile and sculpture, but differ in their narrower umbonal angle and even smaller, more neady square aurcles. This form is, however, at best weakly differentiated ftom the aragonitic shellbed form of eastem North Island, P. "narrow-ribbed triphooki". (e) P. triphooki "Bull Creek form": two moderate sized left valves (ttre only reasonably complete, large specimens seen) from Bull Creek Limestone in Bull Creek, Ruakokopaurna Valley, South Wairarapa, appear to represent a very distinctive form of P. triphooki in which the umbonal angle is very narrow, radial costae are of rounded profile with several fine riblets on their crests and, most distinctive of all, the anterior margin of the anterior auricle is inclined strongly towards the anterior at the dorsal margin, i.e. the auricle is triangular, with its lower margin retracted to the disc, whereas the posterior auricle is small and has an anteriorly inclined posterior margin. This form has not been seen from elsewhere. The apparently greater plasticity of Phialopecten triphooki than of its presumed ancestors possibly reflects either the availability of a wider range of lithologies of Nukumaruan than of earlier ages, or the ability of P. triphooki to live in a wider range of environments than could earlier species. It should be pointed out, though, that this "blooming" of variation was very brief, lasting perhaps only 100 000 years after the onset of markedly cooler conditions at the beginning of Nukumaruan time (as recorded by the migration of Zygochlamys delicatula to central North Island), after which P. triphooki became extinct. The great variation might then be a response fo the unfavourable conditions available to P. triphooki. DISTRIBUTION: The disribution of the several forms of P. triphooki has been outlined above under each form. It occurs in limestone and shallow-water shellbeds of early Nakumaruan age wherever these occur, from Napier o South Wairarapa in eastem North Island and in the Hautawa Shellbed in Wanganui basin. Fleming's (1953) few records from younger rocks in Wanganui basin have been checked, and are all based on fragments or on clearly worn and polished, remanié specimens. AGE: Phialopecten triphooki is restricted to rocks of early Nukumaruan age, in a zone where it occurs together with Crassostrea ingens and Zygochlamys delicatula. This brief range occupied perhaps only the first 100 000 years of Nukumaruan time.» BEU, A. G. 1995. Pliocene Limestones and their scallops. Lithostratigraphy, pectinid biostratigraphy, and paleogeography of eastern North Island late Neogene limestone. Institute of Geological & Nuclear Sciences Monograph 10. Institute of Geological and Nuclear Sciences, Ltd., Lower Hutt, New Zealand, 243 p. [p. 42, 44, 46]
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Phialopecten triphooki (Zittel), form "narrow-ribbed triphooki"; A. G. Beu, 1995, Pliocene Limestones and their scallops, figure 18b.
Phialopecten triphooki (Zittel) sensu stricto; A. G. Beu, 1995, Pliocene Limestones and their scallops, figures 19a-d.
Phialopecten triphooki (Zittel); A. G. Beu, 1995, Pliocene Limestones and their scallops, figures 20a, c, d, form "narrow-ribbed triphooki"; figure 20b, 'Otope Road form."
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«As interpreted here, the subspecies Chlamys (Phialopecten) triphooki triphooki is the latest, largest, and most coarsely ribbed end member of the lineage (height 54-175 mm in 31 Mangapanian shells, mean 128.8 mm; 16-26 ribs on 31 Mangapanian shells, mean 20.4). Primary radial ribs of the right valve are very broad, with square edges, flat or gently convex upper surfaces, moderately strong and numerous, narrow longitudinal grooves to extremely weak, ill-defined surface sculpture, and interspaces ranging from markedly narrower than the ribs to about the same width as the ribs. Primary radial ribs of the left valve are as high as those of the right valve but relatively very narrow, so that in many specimens they are higher than wide; their interspaces are usually wide compared with the ribs, wider than interspaces in the right valve, and sculptured with numerous secondary and tertiary riblets; and the rib surfaces are strongly convex and weakly and closely sculptured with narrow longitudinal grooves and riblets. The left valve is always markedly more strongly convex than the right. The ears are larger than those of other subspecies, and anterior and posterior ears are almost equal in size because of reduction in depth (and presumably lack of use in adulthood) of the byssal notch and byssal sinus . The shells are larger, more coarsely and sparsely ribbed, the ribs with finer and more numerous surface sculpture, interspaces with finer and more numerous secondary and tertiary sculpture, more strongly inequivalve, and with more nearly equilateral ears than in any preceding subspecies.
The subspecies is much more variable than the earlier subspecies. Shells such as the holotype of Phialopecten thomsoni Marwick and a large right valve from N124/f515, GS 5422, Gorge Stream, Patoka (Fig. 26 ) are larger, broader, and have fewer and more irregularribs than any other specimens of Phialopecten, and were regarded by Marwick (1965) as a species distinct from C. (P.) triphooki. Some of the variation described above is shown by shells from the Te Aute Limestone (sensu stricto) of the Raukawa Range that are of the same age as the holotype of P. thomsoni and were collected along the strike from it, in the same rock body. All the specimens from a Phialopecten shellbed (N141/ f1616, GS 11 285, Argyll Road, Otane) are right valves with broad but extremely low, flat ribs (Fig. 24) . Specimens from Amner's lime quarry at Pakipaki (N134/f502 and 502A, GS 4965 and 5424) have moderately broad, well raised ribs that are more coarsely dissected into riblets than on most other specimens seen (Fig. 22). Other Mangapanian collections from Wanganui basin (N138/f446, GS 4208, Wilkies Shellbed, Kauarapaoa Valley-Fig. 29; N124/f516, GS 4124, Wilkies Shellbed, mouth of Waitotara River-Fig. 28) and a Nukumaruan right valve from Napier (N134/f470, GS 576, Lower Scinde Island Limestone; Fig. 23) are very similar, having large, square-section ribs, only slightly less prominent than those of typical P. thomsoni. Specimens from the Lower Scinde Island Limestone at Napier (topotypes of Pecten triphooki Zittel) are relatively small (83-119 mm high in 12 specimens; mean 106.4 mm) with narrower and slightly more numerous radial ribs than those of Mangapanian specimens (18-27 in 12 specimens; mean 22.1), but the range and average number of ribs are raised by a single aberrant left valve from Napier with 27 narrow, well-raised, closely spaced radial ribs. Other Napier specimens have fewer, broader ribs than this extreme variant, and most of them closely resemble Mangapanian specimens from Amner's quarry, Pakipaki. The left valve with 27 ribs was one of few well-preserved left valves from Napier available to Marwick (figured by Marwick 1965, pI. 2, fig. 1) and influenced his opinion that the coarsely ribbed Mangapanian form was a distinct species (J. Marwick, pers. comm.). In a single incomplete paired specimen from Napier (N124/f468, GS 194, "from the lower limestone on the seaward side of Scinde Island, Hawkes Bay County", A. McKay's MS notes) the right valve has 21 primary ribs that widen markedly near the ventral margin to bear four strong riblets on their outer surfaces (Fig. 25) and the left valve has a similar number of high, narrow, widely spaced, finely subdivided ribs, so that the specimen closely resembles Mangapanian shells of the thomsoni form from Waipukurau and from Wilkies Shellbed in Wanganui basin. In the scatter diagram comparing height with numbers of radial ribs (Fig. 1), Nukumaruan shells are shown to be almost entirely enveloped by the range of variation of Mangapanian ones, the one Nukumaruan specimen lying outside the Mangapanian field being the left valve with 27 ribs, described above. The number of ribs on Nukumaruan shells falls almost entirely within the range of variation of Mangapanian ones, and it is concluded that Nukumaruan shells are merely immature specimens of the same taxon as occurs in Mangapanian rocks. The variation encompasses both topotypes of Pecten triphooki and the holotype of Phialopecten thomsoni, and so the name Phialopecten thomsoni Marwick, 1965, is here synonymised with Chlamys (Phialopecten) triphooki triphooki (Zittel, 1864). The status of Pecten accrementa Hutton, 1873 is more difficult to resolve. Boreham (1965, p. 24) noted that, "No other specimen quite like the holotype of Phialopecten accrementa has been collected. Probably it is a left valve of P. triphooki, which is common in the lower Napier Limestone and is very variable in sculpture." She tentatively retained it as a species. Marwick (1965, p. 22) also noted that "although many examples of Phialopecten have been collected from Napier and the surrounding district, no specimens closely agreeing with the type have been found." Hutton (1873, p. 31) gave as localities "Napier; Awatere; Motunau (L): Mount Caverhill." The lectotype is the specimen from Napier. The attached matrix is a hard, yellow-grey, shelly coquina limestone with numerous dark sand grains, in my experience matched in "Te Aute Limestone" lithologies only by the Lower Scinde Island Limestone at Napier. There can be little doubt that the locality is correct. The lectotype (Fig. 21) is a left valve with only 19 primary ribs, which are relatively narrow, widely spaced, and extremely low, with interspaces wider than the ribs and with rib margins sloping outwards to merge gradually into the interspaces. There is a single high, relatively narrow, secondary rib in the centre of each interspace, and fine tertiary riblets are developed in a few interspaces. The lowness, ill defined edges, and wide interspaces of the radial ribs and the clearly defined single secondary ribs give the specimen an unusual appearance. A specimen from N134/f502A, GS 5424, Amner's lime quarry, Pakipaki (Te Aute Limestone sensu stricto, Mangapanian), occurring with large, typical, strongly ribbed specimens of C. (P.) triphooki triphooki, is a right valve with very low ribs over the outer part of the disc, and the ribs are subdivided into three or four relatively prominent riblets, of about the same strength as the secondary riblet in each interspace. Despite being a right valve, the specimen resembles the lectotype of Pecten accrementa, a left valve. The marked convexity of the lectotype and the shape of the posterior ear (the anterior is missing) and of the disc agree closely with those of Chlamys (Phialopecten). Therefore, it is considered that the lectotype of Pecten accrementa is an extreme variant of C. (P.) triphooki triphooki in which the ribs of the left valve are lower and have less well defined edges than usual, and the name Pecten accrementa Hutton, 1873 is here synonymised with Chlamys (Phialopecten) triphooki triphooki (Zittel, 1864). Specimens from the other localities listed by Hutton (1873, p. 31) for Pecten accrementa are either now lost or referrable to other species. AGE OF TYPE LOCALITY OF Chlamys (Phialopecten) triphooki triphooki: Boreham (in Kingma 1971, p. 91) listed Mollusca then known from the Lower Scinde Island Limestone (proposed informally by Kingma 1971), listing among others Phialopecten triphooki, Crassostrea ingens (Zittel), and "?Pelicaria fossa (Marw.) (Cast) ", Kingma (1971, p. 146) noted, "The limestone is typical of the Nukumaruan in the subdivision . . ., consisting of recrystallised, often dark blue, shell casts. It closely resembles limestones at Fernhill (N134/185275), Roys Hill (N134/150350), and further south in the Raukawa-Washpool district, which are undoubtedly younger than the Waitotaran Te Aute limestone." He mapped the Lower Scinde Island Limestone as the lowest limestone bed in Nukumaruan rocks throughout central Hawkes Bay. The age is confirmed by the recent collection of a large Nukumaruan molluscan fauna (N124/f1005, GS 11 109) from the cemented shelly base of the Lower Scinde Island Limestone at Milton Road, Napier, that includes the Nukumaruan index Struthiolaria (Pelicaria) convexa fossa Marwick and several other typically Nukumaruan species (Beu in Hornibrook & Grant-Taylor 1973, p. A23). TYPE LOCALITY: Napier [i.e., Lower Scinde Island Limestone]; "named after Mr Triphook of Ahuriri" (Zittel 1864, p. 52) [T. D. Triphook was a wellknown early surveyor]. The holotype of Pecten triphooki is in the "Novara" collections of the Museum of Natural History, Vienna, reg. number 1959/335/43 (Flügel 1959, p. 838) and was figured by Zittel (1864, pl. 11, fig. 4), Fleming (1965, fig. 7, centre top fig.) and Marwick (1965, pl. 3, fig. 9). Plaster casts are held by N.Z. Geological Survey. Fleming (in Flügel 1959, p. 843) discussed the type locality and restricted it to Milton Road, Napier. The lectotype of Pecten accrementa Hutton (TM2817) and the holotype of Phialopecten thomsoni Marwick (TM2682) are in N.Z. Geological Survey. The subspecies is known from Mangapanian and early Nukumaruan rocks throughout Wanganui basin, Wairarapa District, North Canterbury and, in particular, Hawkes Bay. It is recorded from 31 Mangapanian and 10 early Nukumaruan localities in Te Aute limestone facies from Te Whaka Trig. Station, south of NapierTaupo Road, to Eketahuna.» BEU, A. G. 1978. Taxonomy and biostratigraphy of large New Zealand Pliocene Pectinidae (Phialopecten and Mesopeplum). New Zealand Journal of Geology and Geophysics, 21: 243-269, figs. 1-30. [p. 254, 257, 259]
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Chlamys (Phialopecten) triphooki triphooki (Zittel); A. G. Beu, 1978, Taxonomy and biostratigraphy of large New Zealand Pliocene Pectinidae, figure 9, juvenil (above); figure 19 (below).
Chlamys (Phialopecten) triphooki triphooki (Zittel); A. G. Beu, 1978, Taxonomy and biostratigraphy of large New Zealand Pliocene Pectinidae, figures 21, 22.
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«REMARKS: No other specimen quite, like the holotype of Phialopecten accrementa has been collected. Probably it is a left valve of P. triphooki, which is common in the lower Napier Limestone and is very variable in sculpture.»
BOREHAM, A. U. E. 1965. A revision of F. W. Hutton's pelecypod species described in the Catalogue of Tertiary Mollusca and Echinodermata. New Zealand Geological Survey Paleontological Bulletin, 37: 1-125, pls. 1-20. [p. 24]
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Phialopecten accrementus (F. W. Hutton, 1873); A. U. E. Boreham, 1965, A revision of F. W. Hutton's pelecypod species described in the Catalogue of Tertiary Mollusca and Echinodermata, plate 7, figure 1.
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