Somalipecten wylliei (Cox, 1929)
COX, L. R. 1929. Notes on the Post-Miocene Ostreidae and Pectinidae of the Red Sea region, with remarks on the geological significance of their distribution. Proceedings of the Malacological Society of London, 18: 165-209, pls. 11-13. [p. 199, pl. 13, figs. 4a, 4b]
1929 Chlamys (Aequipecten?) wylliei Cox, 1929
L. R. Cox, 1929, plate 13.
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«Specific Characters.—Shell suborbicular, with the length and height nearly equal,
subequilateral. Left valve moderately inflated, with five very wide and
depressed ribs, which are obscurely nodose near the umbones; interspaces of the
same width as the ribs. Entire surface ornamented with fine radial threads,
crossed by still finer growth-threads. Ears fairly large. Interior with six
wide, flattened ribs (of which the two lateral ones are obscure), corresponding
to the external interspaces, and each limited by a pair of narrow, prominent
ridges; traces of an additional ridge exist on top of two of the wide ribs.
Hinge-plate with two pairs of strong, divergent cardinal crura, the lower of
which are rather oblique: a third, and smaller crural ridge present on the
anterior side of the ligament-pit, parallel to the lower of the stronger ridges
; margins of ligament-pit not sharply defined. Auricular crura inconspicuous. Original
colour of shell apparently pinkish. Eight valve unknown.
Dimensions.—Length, 49 mm.; height, 49 mm.; inflation (left valve), 8 mm. Type Material.--The holotype only (L. 37888), a left valve. Comparison with Other Species.—Externally, this species is remarkably similar to some varieties of the living Mediterranean species, Ch. proteus (Solander), which some authors have united with Ch. glaber (Linne). In Ch. proteus, however, the ears are smaller and the ribs are not nodose near the umbones; the shell is also thinner. When the interiors of the two species are compared, more important differences are seen. In the Mediterranean form the internal ridges number 19 or 20, and are distributed in a very variable and irregular manner, so that they rarely limit definite internal ribs which occur in the positions of the wide interspaces of the exterior of the shell. They seem to correspond to the ten external ribs of the more regular specimens of Ch. glaber, which in some extraordinary manner have all become confused with one another. In the new Red Sea species there are ten internal ridges which limit well-defined ribs, and about two extra ones. The hinge-regions of the two species also differ greatly. In the Mediterranean form there are no strong divergent cardinal crura, such as characterize the new species, the hinge-plate being narrow, with its inferior margin formed by a ridge nearly parallel to the hingemargin; a further difference is that the posterior auricular crus is more prominent. Ch. pes-anatis (Reeve), from the Moluccas, is another form which resembles the new species in its external appearance; but in its numerous, irregularly distributed internal ridges, and its parallel-sided hinge-plate, without any strong, divergent crural ridges, it differs in the same characters as does the Mediterranean form just discussed, to which it appears to be closely related. Finally, Ch. subplicata (G. B. Sowerby), which has been recorded from Aden, differs from the new species in its narrower form, its thicker and more irregular shell, and in the details of its cardinal crura; it has several small, transverse ridges, which are similar to those of Ch. plica, but less conspicuous. Occurrence.--Jebel Titaweb (Sudan Coast), 20 feet raised beach (Wyllie-Lees Coll.). Specific Name.—The species is dedicated to Mr. B. K. N. Wyllie, of the Exploration Staff of the Anglo-Persian Oil Co., Ltd., and a member of the party that collected it.» LESLIE REGINALD COX, 1929
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