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 Agathistegua,\ 
Finally in the Entomostegiia\ 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 exhibit a sort of trellis. 
Vaginulina, to ■which belongs the Nautilus legumen, Gin. Plane., I, f. 7 ; 
Encycl., pi. 465, f. 3. 
Margixulina, -where we find the Nautilus raphanus, Gin. Soldan., II, xciv. 
Planularia, such as the Nautilus crepidulus, Fich., and Moll., XIX, g, h, i. 
Pavonina. 
* M. D’Orbigny has seven genera of Enallostegae : 
Bigenerina, 
Textularia, 
VULVULIXA, 
Dimorphina, 
POLYMORPHINA, 
ViRGULlNA, 
Spheroidixa. 
t The Agathistegua or Milliola of authors, which compose immense banks of 
calcareous stone, in the arrangement of M. D’Orhigny, only form si.\ genera ; 
Bilocui.ixa, 
Spiroloculixa, 
Triloculixa, 
Articulixa, 
(iUIXGUELOCULIXA, 
Adelosixa, 
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. 
+ The Entomoslegua resemble, externally, several of the Helicostegua. M. D’Orb. 
divides them into five genera : 
Amphistegyxa, 
Heterostegyxa, 
Orbiculixa, 
Alveolixa, 
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 Cephalopodes, inserted by M. D’Orbigny the Ann. des Sc. Nat., 
1826, tome YII, p. 95 and 245, and may profit by the large models constructed by 
this able observer. 
