CEPHALOPODA. 19 



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 Agathistecjua.\ 



Finally in the Entomosteyua\ the cells are not simple as in the other 

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

 section of the shell exliibit a sort of trellis. 



Vaginulina, to which belongs the Nautilus legumen, Gm. Plane, I, f. 7 ; 

 Encycl.,pl. 465, f. 3. 



Marginuhna, -where we find the Nautilus raphanus, Gm. Soldan., II, xciv. 



Plaxularia, such as the Nautilus crepidulus, Fich,, and Moll., XIX, g, h, i. 



Pavoxixa. 



* M. D'Oibigny has seven genera of Enallostegie : 



BlGEXERIXA,. 



Textularia, 

 Vulvulixa, 



DiMORPUINA, 



polymorphina, 



Virgulina, 



Spheroidina. 

 f The Ayathistegua or Milliola of authors, which compose immense banks gf 

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



Biloculixa, 



Spiroloculixa, 



Triloculina, 



Articulina, 



q'jinqueloculina, 



Adelosina, 



M. de Blainville 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. 



X The Entomostegua resemble, externally, several of the Helicostegua, M. D'Orb. 

 divides them into five genera : 



Amphistegyna, 



Heterostegyna, 



Orbiculixa, 



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 C^phalppodes, inserted by M. D'Orbigny the Ann. des Sc. Nat., 

 1826, tome VII, p. 95 and 245, and may profit by the large models constructed by 

 this able observer. 



c 2 



