Maclearnia dubrisiensis (H. Woods, 1902)
WOODS, H. 1899-1903. A monograph of the Cretaceus Lamellibranchia of England. Vol. I: 1-232, pls. 1-42. Paleontological Society Monograph. The Paleontographical Society. [p. 162, pl. 29, figs. 8a-8c]
1902 Pecten (Camptonectes) dubrisiensis H. Woods, 1902
H. Woods, 1899-1903, plate 29.
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«Description.— Shell ovate, height a little greater than length, almost equilateral, margins evenly rounded. Umbones pointed. Apical angle about 117º. Ears rather large, unequal.
Right valve flattened, nearly smooth, with a few radial ribs near the antero-dorsal border, and occasional fine curving radial ornamentation like that on the left valve. Antero-dorsal margin slightly concave. Anterior ear long, with a deep byssal sinus, very sinuous growth-lines, and well-marked growth-ridges. Posterior ear triangular, with radial ribs and grooves. Left valve moderately convex— the convexity greatest in the dorsal third, the ventral portions more compressed. Greater part of the surface smooth or nearly smooth; a few faintly marked growth-lines. Ornamentation seen on the sides of the umbonal region, also at the ventral edge, and for a short distance on the inner margin of some of the growth-lines; it consists of faintly marked outwardly curving ribs, separated by very narrow grooves, which are somewhat irregular and (in well-preserved specimens) punctate. Anterior ear large, not sharply separated from the rest of the valve, ornamented by a continuation of the radial ribs and grooves of the umbo, some of which cut the dorsal margin obliquely; the ribs are crossed by faint growth-ridges. Posterior ear smaller with similar ornamentation. Measurements:
(1) Totternhoe Stone, Cherry Hinton.
(2) Chalk Marl, Burham. (3) Totternhoe Stone, Burwell. (4) H. subglobosus zone, Hitchin. Affinities.— The ornamentation is much less developed than in P. striatopunctatus; the shell is also larger, with a wider apical angle, less elevated ears, and with the left anterior ear indistinctly limited.
Remarks.— This is a comparatively rare form, which appears to be confined to the Chalk Marl and the zone of H. subglobosus. Type.— Chalk Marl of Dover, British Museum, No. 38243. Distribution.— Chalk Marl of Dover and Blue Bell Hill, Burham. Totternhoe Stone of Cherry Hinton and Burwell. Zone of H. subglobosus of Hitchin. Lower Chalk of West Row near Mildenhall, and Stoke Ferry.» HENRY WOODS, 1902
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«Description. Medium- to large-sized, almost orbicular shell covered by light concentric ornament; relatively large and long anterior auricles.
Remarks. Distinguished from other species in that the greater part of its disc is smooth and only near the margins of the shell is the concentric ornament pronounced. Size serves to separate it from the much larger and older Early Cretaceous C. (M.) cinctus (J. Sowerby); the much smaller C. virgatus (Nilsson) (Cenomanian-Campanian), which has a coarser microstructure of diverging striae; and the much smaller Cenomanian ?C. milleri (J. de C. Sowerby) from Kent in which the Camptonectes sculpture is less pronounced and its diverging lines are almost straight and rarely divide. Occurrence. Lower and Middle Cenomanian, H. subglobosus Zone; south-east England and Cambridgeshire.» CLEEVELY, R. J. & N. J. MORRIS. 2002. Introduction to molluscs and bivalves. In A. B. Smith & D. J. Batten (Eds.): Fossils of the Chalk, 99-160. The Paleontological Association. London. [p. 123, 124]
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Camptonectes (Mclearnia) dubrisiensis (H. Woods); R. J. Cleevely & N. J. Morris, 2002, Introduction to molluscs and bivalves, plate 21, figure 1.
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«The large size and the small narrow auricles of this species make it more akin to Pecten cinctus than to Pecten lens, and thus its correct name should be Camptonectes (Boreionectes) dubrisiensis (WOODS, 1902).»
DHONDT, A. V. 1972. Systematic revision of the Chlamydinae (Pectinidae, Bivalvia, Mollusca) of the European Cretaceous. Part 1: Camponectes. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, 48 (3): 1-60, pls. 1, 2. [p. 42]
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