160 MACTRIDA. 
ging ribs ; cardinal teeth of the left valve close together, those of 
the ‘right valve separated ; lateral teeth small, 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. (cx, 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. 
CarpiLtA, Deshayes, 1835. 
Syn.—Hemicyclonosta, Deshayes. 
Distr.—2 sp. Chinese Sea, Moluccas. Fossil, 2 sp. Eocene—; 
France, Piedmont. C. Martinii, Desh. (cx, 15>. C. semisulcata, 
ham. (ex, 16). °C. inernus, Desh: (ex; U7). 
Shell oblong, 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 sear long, witha pedal sear 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), S/. Liscav- 
wensis. It has the general appearance of a Cardilia, but the 
hinge differs, and as the teeth are flat, the upper one appears to 
indicate, by its form, that it had supported a cartilage. Giebel 
Says font an eomal ligament is also present, but it must have 
‘been rather thin, for the fulcra are not perceptibly thickened. 
HerTEROcARDIA, Deshayes, 1854. 
Distr.—3 sp. Philippines. A. gibbosula, Desh. (cx, 18). 
Shell oval, subtrigonal, concentrically striate, gap ne poste- 
riorly ; beaks small; hinge narrow; cardinal Tamei iL narrow, 
canaliculated ; pallial impression with a very deep ‘sinus, 
extending as far as the anterior muscular impression. 
Prerops:s, Conrad, 1860. 
Distr.—P. papyria, Conr., (ex, 19). Eocene; Ala., So. Car- 
olina. 
Shell thin, ovate, equivalve; hinge-plate very broad, with an 
ovate cartilage-pit; anterior cardinal tooth very large and 
