96 CEETACEOUS PELECYPODA 



b. Suh-famili/,~FHARELLINJ^. 

 The animals of this sub-division have the siphons generally separated, some- 

 times of very great length, the foot is clavate ; the shells are thin, more or less 

 ovate, and the hinge provided with numerous long teeth, which, however, often 

 become obsolete with age. The genera here included are more numerous than 

 those in the previous sub-fami]y ; they are, as already stated, mostly brackish water 

 forms. 



7. Ceratisolen, Eorbes, 1848, fPharus apud H. and A. Adams, Gen., II, p. 343 ; 

 Folia, d'Orb). Valves thin, hinge with a radiating rib below; in the right valve 

 with three teeth, the posterior very small, the central broadly bifurcate ; in the left 

 valve with two distant teeth, the smaller one near the ligament. 



It is, I believe, quite correct, that the name JPharus be replaced by another 

 one, inasmuch as the former has been already used in another branch of descriptive 

 Natural History. Homes in his admirable work on the Bivalves of the Vienna 

 basin introduces d'Orbigny's name PoZm, but this name is no doubt also obiec- 

 tionable, not only because it is very easily mistaken for Follia, Gray, (a genus of 

 the MuRiciJD^?), but Gray himself occasionally writes the Gastropod name also 

 Folia, (see index to vol. IV of Mrs. Gray's figures of Mollusca, p. 216). There 

 are only two recent species known, C.legumen^Jjinn., n^nA. (7. scalprum, Gould, of 

 which the former also occurs in miocene deposits at several localities in Central and 

 Southern Europe. 



8. Fharella, Gray, 1854. Hinge with two teeth in the right and three in the 

 left valve, the middle one in the latter bifid, all very thin, laterally compressed and 

 close together ; posterior muscular impression more or less elongated, placed nearly 

 horizontally close to the upper edge, pallia! sinus small. 



Conrad in his above quoted catalogue refers four recent species to this genus. 

 There were lately several fossil species also described, but the dentition of the 

 hinges has not been pointed out. The hinge-teeth are indeed so very thin and 

 fragile, that it is difficult to observe them even in recent shells, unless they have 

 been taken alive. I shall subsequently mention the cretaceous species referable 

 to this genus. 



9. Legumen, Conrad, 1858, (Jour. Acad. Nat. Sc, Phil., 2nd ser., vol. Ill, 

 p. 325). Valve very inequilateral; hinge with two very slender teeth in the right 

 valve under the beak and one posterior very oblique prominent lamelliform tooth. 

 This genus was proposed for a cretaceous species ; the form of the teeth and their 

 position agrees with Novaciilina, but the posterior tooth is not lamelliform in this 

 genus. A character of further importance is stated to be the shortness of the 

 posterior part of the shell, which I have not seen in any of the European or Indian 

 cretaceous species ; it does, however, occur in some of the recent American species 

 of Tagelus, from whiuh Legumen would differ by its dentition, but externally it 

 would seem impossible to distinguish between both of them. 



10. Leptosolen, Conrad, 1867, (Am. Journ. Conch., iii, p. 15). "Elongated, 

 thin in substance, straight, with the dorsal and ventral margins parallel ; plicated 



