CKPHALOPODA. 



Or they may be arranged in two alternate series, when they be- 

 come the Enallostegua*. 



Or a few of them may be collected and united as in a pellet, form- 



ing the AyatMsteyua.\ 

 Finally in the Entot 



Finally in tin' Entomostegua\ the cells are not simple as in the other 

 families, but are subdivided by transverse septa in such a way that a 

 on of the shell exhibit a sort of trellis. 



\ \. INULINA, to which belongs the Nautilus legumen, Gun. Plane., I, f. 7; 

 Encycl.,pl. 465, f. 3. 



MARGINULINA, where we find the Nautilus mjihunus, Gm. Soldan., II, xriv. 



PLANULARIA, such as the Nautilus crtpidulus, Pich., and Moll., XIX, g, h, i. 



PAVONINA. 



* M. D'Orbigny has seven genera of Enallostegse : 



BlGBNERJNA, 



TEXTULARIA, 

 VULVULINA, 



DlMORPHINA, 

 POLYMORPHINA, 



\ "HUM I.IXA, 

 Sl-llKROIDINA. 



t The Agathistegua or Milliola of authors, which compose immense banks of 

 calcareous stone, in the arrangement of M. D'Orbigny, only form six genera : 

 BILOCUMXA, 

 SPIROLOCULIXA, 

 TRI LOCUM 

 ARTICUM 



QUINQUELOCULINA, 



ADELOSINA, 



M. de Blaiiiville assures us that he has ascertained, from observation, that their 

 animal has no tentacula : should this be the case, they are at once greatly removed 

 from the Cephalopoda. 



J The KntiiHwsti-yua resemble, externally, several of the Helicostegva. M. D'Orb. 

 divides them into five genera : 



AMPHISTEGYNA, 



HETEROSTEGYN \. 



ORBICCUN \. 



ALVEOLINA, 



FABULARIA. 



Those who are desirous of penetrating more deeply into the study of this curious 

 portion of Conchyliology, on which our limits forbid us to expatiate, but which 

 may be useful in the investigation of fossil strata, will find an excellent guide in the 

 Table Method, des Ctfphalopodes, inserted by M. D'Orbigny the Ann. des Sc. Nat., 

 182G, tome VII, p. y.5 and 245, and may profit by the large models constructed by 

 this able observer. 





c 2 



