JUKES-BROWNE : ON SOME GENERA OF VENEEID^. 239 



that Fischer did not fix the type of Marcia in the sense of the 

 International rules, and therefore Dr. Dall could not adopt Fischer's 

 type. Further, I think anyone fixing a type must use discretion, and 

 if anyone fixes on a type which is inconsistent with the original 

 definition his action is nullified. For instance, one could not fix 

 a type hy di'awing lots. This seems to me another good reason for 

 rejecting exalhida as type." 



Believing, therefore, that I am free to choose another species as 

 the type of Marcia^ I liave no hesitation in selecting V. pinguis of 

 Chemnitz as that type, this being one of the small natural assemblages 

 of species to which the majority of those in the Messrs. Adams' list 

 belong. It is also the first species of Romer's second section of 

 Hemitapes, that section {testa Icevi) being in fact the very assemblage 

 above mentioned, so that my action merely detaches certain species 

 from Hemitapes and restores them to Marcia. At the same time 

 I agree with Riimer in considering the two assemblages to be closely 

 allied, and to be referable to the same genus, but the generic name 

 will be Marcia, with Hemitapes as a subgenus. 



A further consequence of this alteration is that V. exalhida remains 

 to be dealt with, but it will be more convenient to do so after giving 

 an account of Hemitapes and Katelysia. 



3. Hemitapes, Romer. 



As already mentioned, this name was proposed by Romer in 1864 

 for a group of shells, some of which had previously been referred to 

 Tapes and some to Chione. He did not indicate any particular species 

 as a type, but divided the group into two sections or series under the 

 respective headings of {a) Testa transversim sulcata, {h) Testa Itevis. 



He then gave a list of the species referable to each subdivision, the 

 first species of the {a) series being T. virginea (Linn., non auct.), with 

 the synonyms V. Jlammiculata, Lam., f^. callipyga, Lam. {non Born), 

 and V. rimularis, Lam. From this and from his remarks under the 

 head of T. edulis (Chem.) it is evident that he considered the V. virginea 

 of Linnaeus to be identical with V. flammicidata, Lam., and V. rimularis 

 to be a variety of the latter. 



The first species of his second series {V) is V. pinguis, Chem., and it is 

 clear that Romer saw no essential difference between the two series, 

 except that of the external surface, a smooth shell in the one and 

 a grooved surface in the other. 



A curious mistake was made by Stoliczka in 1871,' that of stating 

 that Romer's type of Hemitapes was T. pinguis, a mistake in which he 

 seems to have been followed by Tryon (1884) and by Fischer (1887), 

 both of whom give T. pinguis as their example of Hemitapes. 



No one seems to have discovered the mistake made by Stoliczka 

 until Dr. Dall studied the Veneridse in 1902, and then in rectifying 

 the one he only fell into another. In his Synopsis of 1902 a wrong 

 date is given for the establishment of Hemitapes, but in his monograph 

 of 1903 the right date and reference are given, and the type is stated 



' Cret. Fauna S. India, vol. iii, p. 144 : Mem. Geol. Siirv. India. 



