150 PEOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



I propose to give some account of all these genera, and to mention 

 the species which have heen or can be referred to them. I have not, 

 however, been able to see the Edwards Collection in the British 

 Museum, and cannot therefore include all the species which were 

 named by Edwards, but many of which have never yet been described. 

 Again, there are many fossil shells which were called Venus or 

 Cytherea by the older writers, but which are now known to belong 

 to other genera ; consequently it will be useful in the first place to 

 give a list of the species which have thus been eliminated from the 

 Veneridae, and need not be considered in the present paper. These 

 are the following : — 



Vemis angulata, Fleming (a Cyprina). 



V. fenestrata, Forbes (a Cardita) . 



V. lineolata. Sow. (a Cyprina). 



V. Nysti, Br. & Corn, (an Eriphyla) . 



V. lucina, Br. & Corn, (an Eriphyla). 



V. striato-costata, Forbes (an Astarte) . 



V. submersa, Sow. (type lost, possibly a Cyprina). 



V. tenera, Sow. (a Lucina). 



V. truneata, Sow. (a Cyprina). 



V. peetenifera, Sow. (an Anisocardia). 



Cytherea Scutellaria, Lam. (a Cyprina). 



II. Desckiption oe Genera and Subgeneea. 

 1. DosiNiopsis, Conrad. PI. VI, Eig. 1. 



This genus was founded in 1864,^ the type being a Lower Eocene 

 fossil to which Conrad gave the name of D. Meehi. The original 

 description was very inadequate, the presence of a posterior lateral 

 tooth not being noticed, and only a left valve being figured. He does, 

 however, mention Cytherea lenticularis, Eogers, as a closely allied 

 species from which D. Meehi differs in being "proportionally more 

 elevated and convex." 



It was not till 1901 that Conrad's type was well figured by 

 Messrs. Clark & Martin,^ who consider it to be merely a variety of 

 the previously described B. lenticularis of Rogers. They adopt the 

 genus Dosiniopsis, but do not give any definition of it ; and they 

 regard B. lenticularis as the type, but do not give any fresh description 

 of it, merely quoting that of Rogers. They state that D. lenticularis 

 "is a moderately thin shell with a weak hinge, while the form described 

 by Conrad is a heavy shell with a broad solid hinge. Every possible 

 gradation between the extremes has been observed." 



Erom the figures given by Messrs. Clarke & Martin it is seen that 

 the older and thicker shells {D. Meehi) are as tall as they are broad, 

 while the thinner form {B. lenticularis) is broader than it is high. 

 Although no mention of the posterior lateral tooth is made in the 

 text, it is shown very clearly in the figures, and it is of course more 

 conspicuous in the shells which have a thick hinge-plate than in 

 those with a weak one. 



1 Proc. Acad. Nat. Sci. Philad., 1863, p. 212. 



2 Maryland Geological Survey: "The Eocene Deposits of Maryland," p. 171, 



pi. XXXV. 



