156 CRETACEOUS PELECYPODA 



Reeve, and D. sj^hcBi'lciila, Romer. Romer in his admirable Monograph 

 (1862-63) describes 103 recent species, (excluding several doubtful ones) ; they 

 have a world-wide distribution. The genus occurs in tertiary rocks, but those of 

 older deposits are, with few exceptions, not certain, although they appear to be 

 represented by other similar forms, such as the two next genera. 



13. Enphyla, Gabb, 1864, (Pal. Calif., vol. i, p. 180). Shell sub-orbicular, 

 moderately compressed, with pointed, approximate beaks, with a deep narrow 

 lunula, ai\d, on the whole, in external character much resembling Dosiukt ; 

 muscular impressions large, but not deeply impressed, pallial sinus moderate, round- 

 ish, slightly ascending ; hinge strong, in the right valve with two cardinal teeth, 

 the central one strong and thick, often grooved, the anterior thinner and marginal ; 

 in left valve also with two cardinal teeth, the sub-anterior thick, the posterior 

 thinner ; one small anterior lateral (lunular) tooth of the left valve fits into a 

 corresponding pit of the right, and another small longish posterior and remote one 

 of this valve into a corresj)onding cavity of the left valve. The best known species 

 is Liicina lenticular is, Goldf., from the cretaceous beds near Aachen. 



This is a very different shell from Dosinia as regards hinge-teeth as well as 

 the form of the pallial sinus. It appears very probable that some of the Jurassic 

 Astarte (A. excavata and others) belong to this genus, but a very careful examin- 

 ation of the hinge and of the pallial line, which is broad, though very faint, and 

 also of its sinus, will be necessary. The hinge-teeth of Eriplvjla closely approach 

 those of Astarte, but these have no distinct lateral teeth, nor a deep lunula or 

 a sinus. 



The genus was first proposed by my friend Gabb for a Californian cretaceous 

 species, H. mnbonata. His figure of the hinge of the two valves and the statement 

 of the presence of a deep lunula leaves no doubt that we have a shell of the 

 DOSiNiiNM before us, and not a species of the Astartidm to which the shell 

 in question was referred by Gabb, though there can be no doubt that on account 

 of the great similarity of both, one may easily be mistaken for the other. 



In the cretaceous rocks there are likely a great many species to be found 

 belonging to the present genus. I will point this out subsequently, particularly 

 when enumerating the species described under the generic name Astarte. Tlie 

 type species, with two others also, occm's in our South Indian cretaceous dejoosits. 



14. Gemma, Deshayes, 1853. Shell small, roundish, smooth, pallial line 

 Avith a deep almost perpendicular sinus ; hinge of right valve with two primary 

 teeth, of the left with three, the middle one of which is by far the thickest. The type 

 of this genus is Venus gemma, Totten; it seems, as already stated, very undesirable 

 that a repetition of the generic and specific name should occur; the present 

 species could be called Gemma Totteniana in the absence of any other synonyms. 

 Venus cerina and (/lob ul us in Reeve's Monograph of Venus are externally closely 

 allied to Gemma, though the latter may I'ather be a Dosinia. In Annals of tlie 

 Lye. of N. York for 1862 Prime describes a Venus f Gemma) Manhattensis (p. 4.82). 

 The form of the shell and its close relation to the fossU Cyprimeria appear to me 

 fully to bear out the present classification. 



