CONCHIFEEA. 499 



Fossil? Miocene — . Europe. (100 species. Lower Silurian — 

 D'Orbigny.) 



? Entodesma (Chilensis), Phil. Shell thin, saxicava-shaped, 

 slightly inequivalve and gaping, covered with thick epidermis ; 

 hinge edentulous ; each valve with a semicircular process con- 

 taining the cartilage. 



PA]srDOEA(Solander), Bruguiere. 



Type, P. rostrata, PI. XXII., Fig. 11. {Pandora, the Grecian 

 Eve.) 



Shell inequivalve, thin, pearly inside ; valves close, attenuated 

 behind ; right valve flat, with a diverging ridge and cartilage 

 furrows ; left valve convex, with two diverging grooves at the 

 hinge ; pallial line slightly sinuated. Outer layer of regular, 

 vertical, prismatic cells, 250 times smaller than those of Pinna 

 (Fig. 217). (Carpenter.) 



Animal with mantle closed, except a small opening for the 

 narrow, tongue-shaped foot ; siphons very short, united nearly 

 throughout, ends diverging, fringed ; palpi triangular, narrow ; 

 gills plaited, one on each side, with a narrow dorsal border. 



Distribution, 18 species. United States, Spitzbergen, Jersey, 

 Canaries, India, New Zealand, Panama; 4 — 110 fathoms, bur- 

 rowing in sand and mud. 



Fossil, 14 species. Carb. — . United States, Britain. 



Myadoea, Gray. 



Type, M. brevis, PI. XXIII., Fig. 12. 



Shell trigonal, rounded in front, attenuated and truncated 

 behind ; right valve convex, left flat ; interior pearly ; cartilage 

 narrow, triangular, between two tooth-like ridges in the left 

 valve, with a free sickle-shaped ossicle ; pallial line sinuated ; 

 itructure like Anatina ; outer cells large, rather prismatic. 



Distribution, 10 species. New Zealand, New South Wales, 

 Philippines. 



Myochama, Stutchbury. 



Type, M. anomioides, PI. XXIII. , Fig. 13. 



Shell inequivalve, attached by the dextral va.ve and modified 

 by form of surface of attachment ; posterior side attenuated ; 

 left valve gibbose; cartilage internal, between two tooth-Uke 

 projections in each valve, and furnished with a movable ossicle,' 

 anterior muscular impression curved, posterior rounded, pallial 

 sinus small. 



Animal with mantle-lobes united; pedal openuig and siphon • 



