Pecten difformis Odhner, 1917
ODHNER, N. H. 1917. Results of Dr. E. Mjöberg's Swedish scientific expeditions to Australia 1910-1913. Part 17. Mollusca. Konglica Svenska Vetenskaps-Akademiens Handlingar, 52 (16): 1-115, pls. 1-3. [p. 15, pl. 1 figs. 4, 5.]
«P. difformis n. sp. (Pl. 1, figs. 4, 5). Shell highly compressed, of a broadly ovate shape, truncated above by a straight extended hinge line. Anterior margin nearly perpendicular, with a slight sinuation above the middle, inferior one well rounded and posterior slightly curving. No distinct ears on the upper valve. Umbones triangularly projecting somewhat behind the middle of the hinge line, defined by a feeble radiating impression behind and a more distinct one in front. Inferior valve somewhat smaller and flatter than the upper one, with a deep byssal sinus, bounded by a straight anterior margin of the valve, with a few denticles above and an S-formed curvation of the lower margin of the wing. Sculpture of both valves consisting of very fine radiating lines, more conspicuous towards the margins; the wing of the inferior valve with stronger radiating lirae. Colour hyaline with radially stretched snowy dots spread all over. Maximal dimensions: height 10.2 mm; breadth (from anterior to posterior margin) 8.9 mm; thickness of the closed shell 1.9 mm. Locality: 45 miles W. S. W., 6 small sps with dried animals, attached to the basal part of a Turbinaria.
Though certainly not full-grown, the largest of these specimens has such a peculiar form, aberrant from the normal shape of the Pectinidae, that it must be established as a new species. Above all the absence of ears is a remarkable characteristic. Compared with P. madreporarum PETIT, another species living on corals, the new form is broader at the hinge line, is less oblique and far less tumid, and it has a different, much finer, sculpture.» NILS HJALMAR ODHNER, 1917
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N. H. Odhner, 1917, plate 1.
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