42 Lamarck's Genera of Shells. 



of a loot, in the form of a radiated disc, and furnished with a 

 short pedicle. 



Type. Spondylus gcedcropus . (Idem. Lmw.) 



Shell red above; striae small, longitudinal, close together, 

 rough, granular; from six to eight rows of sublingulate, trun- 

 cated, middle-sized spines. 



Mediterranean. 21 recent species, 4 fossil. PI. 2. Fig. 91. 



7. Podopsis. 



Shell inequivalve, subregular, adhering by the lower beak, 

 inauriculate ; lower valve largest, most convex, and its beak 

 most prominent. Hinge without teeth. Ligament internal. 



The podopsides, which are only known in the fossil state, are 

 similar in some respects to the gryphoea, but are distinguished 

 from them, by the lower beak not being curved either above the 

 upper valve, or over the side. They resemble the pectines by 

 their regularity, by the shell not being foliated, and by their lon- 

 gitudinal stria. They appear to have some relation to the pla- 

 giostoma, but differ from them in being fixed shells, and in want- 

 ing the opposite beaks, with their intermediate, obliquely in- 

 clined facet. The upper valve of the podopsis, which is always 

 shorter than the other, seems to have no beak, in consequence 

 of its not being curved or prominent. 



Type. Podopsis tnmcata *. 



Shell longitudinal, cuneiform, rounded above, suboblique ; 

 strice longitudinal, thin, sometimes rough, with a few prickles; 

 longest beak crenate. 



Tourainc. PI. II. Fig. 92. 



2nd Family, 

 OsTiiACEA. (5 Genera.) 



Ligament internal, or semi-internal. Shell irregular, texture 

 foliated, sometimes papyraceous. 



Almost all the ostracea are irregular shells, of a foliated or 

 lamellar texture, seldom auriculated at the base, and still more 

 rarely radiated externally. 



The animal has no foot, arm, or projecting siphon ; in many 

 ■* Tnmcalai. 



