76 Lamarck's Genera of Shells. 



others. These shells are only known in the fossil state, and were 

 discovered in the Pyrenees, by the late M. Picot de la Peyrouse. 



Type. Hippurites riujosa *. 



Shell cylindrical, attenuated, very thick, transversely rugose ; 

 base truncated ; a double pit in the truncation. Fossil, from the 

 Pyrenees. PI. vi. Fig. 212. 



5. Conilitesf. 



Shell conical, straight, slightly bent ; sheath thin, distinct from 

 the contained nucleus. Nucleus subseparable, multilocular, 

 divided by transverse septa. 



The conilites appears to differ from the belemnites, principally 

 in not having the upper portion of the sheath, or external shell, 

 elongated and solid, (in consequence of the termination of the 

 cavity for the nucleus before it reaches the summit,) as in those 

 shells. The nucleus seems also to be less easily separated from 

 the sheath than that of the belemnites. 



One species. Conilites pyramida ttt%. 



Shell conico-pyramidal ; lotver face concave. Fossil, Coast of 

 Britany. PI. vi. Fig. 213. 



2d Family. 

 Lituolata, (3 genera.) 



Shell partly spiral ; the last whorl straight. 



The lituolata are multilocular shells, of a spiral form, but the 

 last whorl terminates in a straight line. The transverse septa, 

 which form the chambers, are generally traversed by a siphon, 

 which is interrupted before it reaches the succeeding septum. The 

 whorls which form the spiral are, sometimes, distant from one 

 another, leaving a remarkable space between them ; sometimes 

 they are quite close together; in either case, the last always ends 

 in a straight line. Some have the last septum pierced with from 

 three to six holes, as if their siphon were compound. 

 1. Spirula§. 



Shell cylindrical, thin, almost transpaient, white or pearl colour, 

 multilocular, partly twisted into a discoidal spiral ; whorls distant 



* Rugose. t From conns, a cone- 



J Pyramidal. $ A Lttle spire. 



