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Show 934 DR. GWYN JEFFREYS ON THE MOLLUSCA OF THE [Nov. 29, distinctly observable in these as well as in recent specimens. Mr. Dall says that the number of ribs varies from 14 to 17. PHOLADOMYA LOVENI1, Jeffreys. (Plate LXX. fig. 7.) SHELL inequilateral, wedge-shaped, gaping at the posterior end, convex, of a pearly nature, thin, partly semitransparent, lustreless : sculpture, 10-12 longitudinal ribs, besides some intermediate strise ; these are more or less interrupted by strong periodical marks of growth, so as to give the ribs a nodulous appearance; the sides are ribless; the whole surface is covered with minute prickly tubercles : colour white: margins rounded on the anterior side, inclining upwards towards the other side, which is also rounded but slightly truncate, sloping at the hack from each side of the umbo : beaks bluntly triangular, turned inwards ; umbones prominent: ligamental pit in the right valve obtuse-angled, placed outside underneath the beak, and defined outwards by a thin plate : hinge-line sloping towards the posterior side: hinge-plate thin, sinuous, reflected : teeth none: inside highly glossy and nacreous: scars inconspicuous. L. 0-4, B. 0*5. ' Porcupine' Exp. 1870 : Atl. St. 22, 28a ; Med. 55. None of the specimens are quite perfect. One of them indicates twice the size given in the description. That figured is from the ' Josephine' Expedition. , Distribution. Palermo, fragments (Monterosato); 162 fms.: off Marseilles ('Travailleur' Exp. 1881); Villa franca, Azores ('Josephine' Exp.); 320-600 fms. Monterosato doubtfully refers this species to the Thracia pholado-myoides of Forbes from the iEgean ; but Forbes knew too well the hinge-structure of Thracia as well as of Pholadomya to have made such a mistake in the genus. His description is as follows (1844):- "Fam. Pylorida. Genus Thracia, Leach. " Thracia pholadomyoides, sp. nov. " T . testa ventricosd, sinuosd, granulata, concentrice sulcata, sulcis longitudinaliBus paucis (6) decussatd ; umBoniBus acutis. Long. 0T 9 ¥, lat. 1T 9 2 unc. Cape Artemisium (1808)." I cannot guess the meaning of the last figures. Forbes gives also two other species of Thracia, viz. phaseolina and puBescens. I should have been inclined to consider his T. pholadomyoides a young T. covBuloidea but for that part of his description which mentions the decussation of concentric furrows by six longitudinal furrows. P. zanclea of Seguenza, from the Sicilian pliocene formation, is allied to the present species ; but it is more rounded, and is not produced or extended at the anterior side. If our species be that of F\>rbes, the name pholadomyoides would be inappropriate. 1 Named in honour of Professor Loven, the eminent Swedish zoologist. |