JUKES-BROWNE : CRETACEOUS AND EOCENE VENERTDiE. 173 



The two most obvious points of difference are the deep excavation 

 and abbreviation of the hinge-plate in the latter, and the non- bifid 

 character of the right posterior cardinal. Judged by these points, the 

 v. deleta, V. GesUni, V. puellata, and V. quadrata of Deshayes all 

 belong to Venerella, and not to Mercimonia. 



Of V. deleta Deshayes himself says, "la charniere est etroite, et 

 ressemble a celle de nos Fenerupis^' ; he notes the wide separation of 

 the right posterior tooth, which he describes as "etroite allongee et 

 simple." From his figures and those in the more recent " Iconographie 

 Complete " of M. Cossmann, V. GesUni, V. puellata, and V. quadrata 

 appear to have simple teeth. 



18. Tapes, Megerle. 



It is not quite certain whether the genus Tapes, as distinguished 

 from Baroda, is represented in the Cretaceous fauna, but a species 

 described by Zittel {T. Rochehrunei), from the Gosau Beds, does seem 

 from his figure ^ to have the hinge of Tapes. 



The genus Tapes should, I think, be restricted to such shells as 

 can be included in the sections enumerated by Fischer, without any of 

 those which he ranks as subgenera. As thus understood, Tapes has 

 a small hinge -plate bearing three small cardinal teeth in each valve, 

 placed near together, and as a rule only slightly divergent ; moreover, 

 two in the right and one or two in the left valve are grooved or bifid, 

 only the anterior of the right and the posterior of the left being always 

 entire. The bifidness of the teeth is always apparent in young and 

 youngish specimens, though sometimes obscure in old individuals. 



It is interesting to find that three species of Tapes occur in the 

 Eocene deposits. One of these was described as Venus tenuis by 

 Deshayes in 1824,^ and recognized as a Tapes by Pictet in 1855,^ but 

 it is difficult to say whether it belongs to any particular section of 

 the genus. Another species (71 Parisiensis) was described by Deshayes 

 in I860,* and this evidently belongs to the group which is represented 

 in our seas by Tapes aureus, and in the Mediterranean by T. texturatus 

 and others. 



The third species has not yet been described or figured, but has 

 been named T. Comptoni by Edwards, and only one specimen of a 

 right valve is known, this being preserved in the British Museum. 

 For the following account of it I am indebted to Mr. R. Bullen 

 Newton: — "The Tapes Comptoni is a much worn right valve with 

 a fractured anterior margin. Externally it is covered with fine, 

 closely-set radial striations, which are crossed by somewhat distant 

 concentric lines of growth. The internal margins are smooth. The 

 sinus is deep, but its form is somewhat obscure, the marking having 

 the appearance of being angulate, though in reality it may be rounded 



1 " Bivalven der Gosaugebilde in den Nordost Alpen " : Denkschr. k. Akad. 

 Wissensch. "Wien, vol. xxiv (1865), p. 124, pi. iii, fig. 4. 



* Traite de Paleont., 2nd ed., vol. iii, p. 441. 



' Description des coq. foss. des Env. de Paris, p. 143, pi. xxiii, figs. 18, 19. 



* Anim. sans Vert. Bassin de Paris, p. 414, pi. xxix, figs. 5, 6. 



