160 MACTRID^. 



ging ribs ; cardinal teeth of the left valve close together, those of 

 the right valve separated ; lateral teeth SBiall, thin, confounded 

 with the cardinal pit ; ligament subexternal, marginal, not sepa- 

 rated by a lamella from the internal cartilage, which is lodged 

 in a triangular, elongated, shallow pit. L. lanceolata, Gray 

 (ex, 10). 



Anatinella, G. Sowerby, 1829. 



Distr. — 3 sp. Ceylon, Philippines ; sands at low-water. A. 

 Candida^ Chemn. (ex, 13). A. Sibbaldi, Sowb. (ex, 14). 



Shell ovate, rounded in front, attenuated and truncated behind ; 

 cartilage in a prominent spoon-shaped process, with 2 small teeth 

 in front ; muscular impressions irregular, the anterior elongated ; 

 pallial line slightly truncated behind. 



Cardilia, Deshayes, 1835. 



Syn. — Hemicyclonosta, Deshayes. 



Distr. — 2 sp. Chinese Sea, Moluccas. Fossil, 2 sp. Eocene — ; 

 France, Piedmont. G. Martinii, Desh. (ex, 15;. G. semisulcata , 

 Lam. (ex, 16). G. inej-mis, Desh. (ex, lY). 



Shell olDlong, ventricose, cordate ; beaks prominent, subspiral ; 

 hinge with a small tooth and dental pit in each valve ; ligament 

 partly internal, contained in a spoon-shaped inflection •, anterior 

 muscular scar long, with a pedal scar above ; posterior adductor 

 impression on a prominent subspiral plate ; pallial line simple. 



STROTHODON,Giebel. Right valve tumid, high like Cardilia, beaks 

 incurved, with a groove running from the beaks to the posterior 

 margin, hinge with a flat cardinal tooth and with a second tooth 

 projecting from its base below and anteriorly. Only one valve 

 known, from the Triassic beds of Liskau (Germany), St. Lisoav- 

 ieiisis. It has the general appearance of a Cardilia, but the 

 hinge difi'ers, and as the teeth are flat, the upper one appears to 

 indicate, by its form, that it had supported a cartilage. Giebel 

 says that an external ligament is also present, but it must have 

 been rather thin, for the fulcra are not perceptibly thickened. 



Heterocardia, Deshayes, 1854. 



Distr. — 3 sp. Philippines. H. gibbosula., Desh. (ex, 18). 



Shell oval, subtrigonal, concentrically striate, ga;^'ng poste- 

 riorly ; beaks small ; hinge narrow ; cardinal lann 1 a narrow, 

 canaliculated ; pallial impression with a very deep sinus, 

 extending as far as the anterior muscular impression. 



Pteropsis, Conrad, 1860. 



Distr. — P. 2Mpyria, Com: (ex, 19). Eocene; Ala., So. Car- 

 olina. 



Shell thin, ovate, equivalve ; hiuge-plate very broad, with an 

 ovate cartilage-pit ; anterior cardinal tooth very large and 



