HALL : ON THE GENITS GEMMA, DESHAYES. 243 



termination with papillae, is darker, pinkish and longer than the other. 



The siphonal muscles leave a rather elongated erect scar or pallial 

 sinus on the shell, usually angulated in variety tottenii, but more 

 rounded in the vn.ne\.y pit rptire a. 



The foot is of the usual shape, rather long and narrow, slightly 

 marginated below. 



The lunular boundary, though faint, is traceable and encloses a 

 cordiform space extending over two-thirds of the way from the beaks 

 to the anterior end of the valves. The figures indicate its proportion. 



The animal is viviparous, living near the shore or between tide- 

 marks, on a sandy or muddy bottom. No species is positively known 

 except from Eastern North America, but lately specimens have been 

 obtained from ground in California, where eastern "seed" oysters had 

 planted, and where the species has evidently been introduced with the 

 mud adhering to the young oysters. 



The nearest relative of Gemma is the genus Parastarte Conrad, 

 1862, which differs chiefly by its obsolete pallial sinus, and the ab- 

 sence of the left posterior cardinal tooth. Concurrently the lateral 

 grooving of the margins is less distinct and it is probable that the 

 siphons are reduced to mere orifices. 



On the Pacific coast we find taking the place of Gemma the little 

 genus Psephis Carpenter, 1864, a name preoccupied ten years earlier 

 in Lepidoptera by Guenee, and which I propose to replace by Pse- 

 phidia. Carpenter's type was P. lordi Baird from the Vancouver 

 district. It has three simple unsulcate cardinal teeth in each valve, 

 while the anterior left and posterior right dorsal margin, outside the 

 hinge plate, is grooved to receive the bevelled edge of the opposite 

 valve ; the inner margins of the valves are not crenate, and there is a 

 well-marked rounded pallial sinus. The little Venus tantilla of Gould, 

 which has been widely distributed under the name of Psephis^ has a 

 different hinge from P. loi'di, and cannot remain in the same genus. 

 It is very close to Transen>tella. 



The three genera above cited will form a sub-family of Veneridae, 

 which I have called Gemmince, characterized by small size, viviparity, 

 and other less striking characters. So far as known it is an exclu- 

 sively American group and is represented in our Tertiaries as early as 

 the Oligocene. 



Cyprina v. Cypriniadea. — Referring to Mr. Hoyle's note (antea p. 214) I 

 should like to say that besides the derivation theory for the retention of both 

 Cyprinns and Cyprina in zoological nomenclature, we have to consider distincive- 

 ness of name. To prevent confusion, therefore, in the compilation of faunal lists 

 it is certainly a judicious policy to favour the adoption of Cypriniadea — R. BuLi.EN 

 Newton. 



