Neithea inconstans (Sharpe, 1850)
SHARPE, D. 1850. On the secondary dístrict of Portugal, on the North of the Tagus (on secondary rocks of Portugal). The Quarterly Journal of the Geological Society of London, 6: 135-201, pls. 14-26. [p. 188, pl. 19, figs. 3a, 3b]
1850 Pecten (Janira) inconstans Sharpe, 1850
D. Sharpe, 1850, plate 19.
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«Shell heptagonal, nearly circular; convex below, slightly concave above. The lower valve nearly hemispherical, with an incurved umbo, ornamented with about twenty elevated, rounded, nearly equal ribs, separated by unequal rounded hollows, in some of which there are one or two fine ribs. Every fourth rib is longer than the rest, and is produced into the angles of the shell; some of these longer ribs are also more elevated than the rest.
Upper valve slightly convex, covered with seventy to eighty ribs of varying form and size, separated by very unequal hollows. The principal ribs which run to the three front angles of the shell are divided into four by one broad central furrow, and two slight lateral furrows down each, and they are very unequally elevated, one being always much more prominent than its fellows: towards the lateral angles the ribs are much subdivided and very unequal. Both valves are covered by well-marked concentric lines. Ears small, placed very forward on the upper side of the shell. Diameter 3 to 4 inches. In the upper beds of the hippurite limestone at Lisbon; not common. This is closely related to Pecten quadricostatus, and, as in that shell, every fourth rib on the lower valve is of more importance than its fellows; but on the upper valve the ribs are more angular, and more numerously and irregularly divided than in that species. The most singular feature in the shell is the irregular elevation of the principal ribs, one of the two middle ones being always depressed and the other elevated, which gives a very awkward appearance to the shell: all the specimens seen agree in this respect. The ears are broken in all my specimens. If all M. D'Orbigny's species of Janira are considered distinct, this must also rank as a distinct species; but if farther observation leads us to throw many of those together, then this shell will probably be regarded as only a variety of P. quadricostatus. Plate XIX. fig. 3 a. Upper valve.
Fig. 3 b. Side view of the same specimen.» DANIEL SHARPE, 1850
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«Material:
- One incomplete right valve from Monte Candole (southern side of the Monte Cavallo massif, 6 km NE of the Col dei Schiosi fossiliferous locality, western Friuli) [DGP 26727: H = 57 mm; L = 58 mm; B'= (18) mm]. - One poorly preserved right valve (MSNT 11832) from Groznjan (= Grisignana), Istria, Croatia, original of Parona (1926). - One small incomplete bivalved specimen (MSNT 11833) from Sovinjak (= Sovignacco), Istria, Croatia. Discussion: The right valves are relatively convex; the left valve of the small bivalved specimen from Sovinjak is moderately concave. The rib distribution, as already noted by Parona (1926), is comparable to that figured by Choffat (1902, pI. 2, figs 5,6). The material at our disposal does not warrant further comments.
The specimens from central Italy assigned to this taxon in literature have not been seen by us. The Parona (1918) specimen is neither described nor illustrated. A valve from the Lepini Mts. (Latium) is discussed and illustrated by Sirna in Praturlon and Sirna (1977) (data later re-used in Carbone et al., 1981 and in Carbone and Sirna, 1981). Despite what is claimed, we think that because of its subequal ribs and of its shape, this specimen cannot be considered as belonging to Neithea inconstans. Its probable total rib number (20) and the distribution of the ribs make it a very likely N. (N.) hispanIca (d'Orbigny, 1850), but without seeing the specimen we cannot at the present time be completely certain about its specific attribution. Distribution: Described only from Cenomanian rudist formations [Portugal, NE Italy (Friuli), Croatia (Istria) and western Serbia, always associated with N. (N.?) fleuriausiana] (Text-fig. 5).»
DHONDT, A. V. & I. DIENI. 1993. Non-rudistid bivalves from Late Cretaceous rudist limestones of NE Italy (Col di Schiosi and Lago di S. Croce areas). Memorie di Scienze Geologiche, 43: 165-241, pls. 1-20, text-figs. 1-18. [p. 192, 194]
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Neithea (Neithea?) inconstans (Sharpe, 1850); A. Dhondt & I. Dieni, 1993, Non-rudistid bivalves from Late Cretaceous rudist limestones of NE Italy (Col di Schiosi and Lago di S. Croce areas), plate 5, figures 7, 19.
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