ANATINID^. 143 



digitiform foot ; the siphons are more or less prolonged, united 

 in their entire length or only at the base, and the united portion 

 of these siphons is almost invariably covered with an extension 

 of the shell-epidermis. There is also a small opening in the 

 mantle below, at the base of the siphons. The gills are thin 

 and in many cases (though not invariablj^) single. The palpi 

 are usually long and narrow. 



There is scarcely an}^ other family of Pelecypoda so important 

 to the palaeontologist, being represented throughout the strata 

 from the oldest sedimentary deposits. The species living at the 

 present time may be said to be only the remnants of the group; 

 they are distributed all over the world, but they are nowhere 

 very numerous, and some of them belong to the rarest 3'et 

 known shells. Their maximum of development appears to have 

 been during the Jurassic period. 



{Pandorse.) 



Pandora (Solander), Bruguiere, 1792. 



Etyvi. — Pandora^ the Grecian Eve. 



Syn. — Pandorella, Conrad. 



Diatr. — 24 sp. United States, Spitzbergen, Jersey, Canaries, 

 India, New Zealand, Philippines, Panama; 4-110 fathoms, bur- 

 rowing in sand and mud. Fossil, 14 sp, Eocene — •; United 

 States, Britain. P. oblonga, Sowb. (cviii, 48). P. ineequivalvis, 

 Linn, (cviii, 49). 



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; usually no ossicle ; pallial line slightly sinuated. Outer 

 layer of regular vertical, prismatic cells. 



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. 



KENNERLiA, Carp., 1864. Under this name are separated a feAv 

 species, which still more resemble Myodora, than the true Pan- 

 dorse. The_y all have a thin hinge-ossicle, and the typical species 

 have radiating ribs on the right valve. P. bicarinata, Carp. 



CCELODON, Carp., 1864. The" form of the shell is similar to that 

 of Pandora ; each valve with two hinge-teeth directed towards 

 the anterior adductor muscle, and in the left one they are connected 

 b}'^ a thin lamina; no ossicle or pallial sinus. P. Ceylonica^ Sowb. 

 (cviii, 47). 



CLiDiOPHORA, Carp., 1864. Similar in form to the last ; right 

 valve rather tumid, with three hinge-teeth ; the posterior one 

 elongated ; left valve often with two teeth ; ossicle present. 



