934 DR. G-WYN 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. 



1/ Pholadomya loveniS 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 striae ; 

 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 up- 

 wards towards the other side, which is also rounded but slightly 

 truncate, sloping at the back from each side of the umbo : beaks 

 bluntly triangular, turned inwards ; umbones prominent : ligamental 

 pit in the riglit valve obtuse-angled, placed outside underneath the 

 beak, and defined outwards by a thin plate : hinye-line sloping to- 

 wards 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 ('Jose- 

 phine' Exp.) ; 320-600 fms. 



Monterosato doubtfully refers this species to the Thracia pholado- 

 myoides of Forbes from the jEgean ; but Forbes knew too well the 

 hinge-structure of Thracia as well as of Pholadoimja to have made 

 such a mistake in the genus. His description is as follows (1844) : — 



"Fam. PyloridcE. Genus Thracia, Leach. 

 " Thracia pholadomyoides, sp. nov. 



"T. testa ventricosii, simtosu, granulatu, concentrice sidcatu, 

 sulcis longitudinalibus paucis (6) decussatd ; umbonibus acutis. 

 Long. Ot%, lat. If'*^. 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. corbuloidea 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 plioceiie 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 he that of Forbes, 

 the name pholadomyoides would be inappropriate. 



^ Named in honour of Professor Lovto, the eminent Swedish zoologist. 



