LAMELLIBKANOHIATA FEOM BASE OF UPPER MARLS. 219 



there are two, and most probably three, distinct species among- them, prob- 

 ably generically distinct, there is but little likeliliood of any of them being 

 specifically identical with that one. The form originally described by Mr. 

 Gabb as Dione Dduwarensis differs from this one in its more elongate and 

 more regularly oval form. Mr. Conrad, in the Am. Jour. Conch., Vol. V, 

 PI I, Fig. 6, gives a figure of a shell which he identifies with Mr. Gabb's 

 species, but I think wrongly, although the figure is too poor to aflord con- 

 clusive evidence. This, and at least one other associated form, appears to 

 me most likely to prove to possess the features of Roemer's genus Caryatis; 

 in fact Mr. Conrad has stated that the other one which he refei's to, C. Dela- 

 warensis^zDione Delawarensis Gabb, possesses the hinge structure of that 

 genus, and certainly the general form, rotundity, muscular and pallial mark- 

 ings correspond very closely. They might also with nearly equal propriety 

 be placed under Sowerby's genus Thetis, except for the want of the notch 

 in the pallial sinus. 



Formation and locality. — The species appears to be common in the 

 lower (Cretaceous) layers of the Upper Marls at Farmingdale, Squankum, 

 New Egypt, and at Shark River, New Jersey, and is often found associated 

 in collections with the fossils from the upper or Eocene laj^ers, but I cannot 

 ascertain that it is ever found in these beds. 



SAXICAVID^. 



Geuus PANOPEA Menard. 



Panopea eUiptica, u. sp. 



Plate XXVIII Figs. 24 and 25. 



Shell, as known from the internal cast, transversely elongate, having 

 been fully once and a half as long as high, with narrowly rounded extrem- 

 ities, very ventricose valves, and moderately elevated beaks, which appear to 

 have been directed toward the posterior end of the shell. Anterior end widest, 

 and rather narrowly rounded on the extremity ; posterior end suddenly nar- 

 rowed on the dorsal line near the beaks, the line of the liinge being con- 

 cave ; extremity of the valves narrow and scarcely truncate on the margin, 



