ANATI^fID^. 151 



with an obscure lunette ; posterior hinge-line with a narrow 

 interior ridge ; ligament external. Epidermis strongly wrinkled. 



Animal unknown ; probably had a closed mantle and respi- 

 ratory siiDhons. 



Cyathodonta, Conrad, 1849. 



Diatr. — 4 sp. China, L. Cal., Honduras. G. granulosa^ Ads. 

 and Reeve (cviii, 74). 



Shell like Anatina in form; "hinge with a broad, not very 

 projecting fosset, which is carinated near the margin ; muscular 

 impi^essions rounded, indistinct ; pallia] impression with a large, 

 rounded sinus." 



GrONiOMYA, Agassiz, 1838. 

 • Syn, — Lysianassa, Munst., 1838. 



Distr. — Cretaceous and Jurassic. G. JDnboisi, Agass. (cviii, 75). 



Shell oblong, rather compressed, thin, surface marked about 

 the middle of the flanks with angularly bent stride or ribs ; 

 hinge without teeth ; a slight incision below the beaks, and 

 slightly thickened nymphse beyond the same for the attachment 

 of a ligament are present. 



Ch^engmya, Meek, 1865. 



Syn. — Anoplomya, Krauss. 



Distr. — Cretaceous, Jurassic. G. Gooperi^ Meek (cix, 84). 



Shell oblong, equivalve, inequilateral, thin, concentrically 

 striated or ribbed, with an oblique process below the beaks of 

 each valve, probabl}^ supporting an internal cartilage ; njmiphse 

 prominent for the attachment of an external ligament ; sinus 

 very deep and usually angular. 



Terquem has sufficiently proved that this a good genus, and 

 must be kept separate from Homomya, Myacites and Panopaea, 

 which it externall}^ greatly resembles. 



Shell much like Anthracomya, of thin structure, more or less 

 compressed, posteriorly gaping. 



Pholadomya, G. Sowerby. 



Syn. — Procardia, Meek. 



Distr. — 2 sp. West Indies, off Rhode Island. P. Candida., 

 Sowb. (cviii, 76, 77). Fossil, 160 sp. Lias — ; United States, 

 Europe, Algeria, Thibet. P. e^aZ^a^a, Agass. (cix, 85). P. glabra, 

 Agass. (cix, 86). 



Shell oblong, equivalve, ventricose, gaping behind ; thin and 

 translucent, ornamented with radiating ribs on the sides ; liga- 

 ment external ; hinge with one obscure tooth in each valve ; 

 pallial sinus large. 



Animal with a single gill on each side, thick, finely plaited, 

 grooved along its free border, the outer lamina prolonged dor- 

 sally ; mantle with a fourth (ventralj orifice, — Owen. 



