124 MR. OWEN’S DESCRIPTIONS OF 
cative of modifications of the shell, which he terms ‘ Protector’. The Seiches, or Naked 
Cephalopods of Cuvier, are subdivided into two orders, of which the first, under the name 
of Anosteophora, corresponds with the Poulpes of Cuvier, and with the Octopoda of Dr. 
Leach’s arrangement of 1817, presently to be noticed ; while the second order, Sepie- 
phora, is equivalent to the Decapoda of Leach, or to the remaining Seiches of Cuvier’s 
system. All the Cephalopods with chambered shells are collected together into a third 
order, under the name of Nautilophora. 
The reformed classification of the Cephalopoda contained in the Malacologie of M. De 
Blainville (1825)', though much more truly expressive of the natural affinities of its ob- 
jects than that proposed by Mr. Gray, still reposes on the insecure basis of tegumentary 
modifications. The whole of the Seiches of Cuvier are here raised to the rank of an 
Order, under the name of Cryptodibranchiata ; and the author, guided by the knowledge 
of their internal organization, rightly uses the characters derivable from the modifica- 
tions of their internal shell, as indicative merely of the subdivisions of this order. M. 
de Blainville made also another important step in advance, by separating the Cephalo- 
pods with microscopic chambered shells, under the name of Cellulacea, from those with 
siphonated shells, which he terms Polythalamacea. Subsequent researches have since 
proved that the Cellulacea of M. De Blainville ought to be removed altogether from the 
class Cephalopoda. The classification of the Cephalopods adopted by M. Férussac in 
the great work still in progress of publication is essentially the same as regards its pri- 
mary divisions as that of M. de Blainville, but the nomenclature of M. D’Orbigny is 
preferred. All the Cephalopods, e.g., without chambered shells, form the first order, under 
the name of Acetabuliféres ; all those having siphonated chambered shells form a second 
order, termed Siphoniféres ; and the non-stphonated microscopic chambered shells consti- 
tute a third order, under the name of Foraminiferes. 
Now in consequence of the subordinate character on which all the preceding classifica- 
tions are founded, there is a violation of natural affinities in the formation of the primary 
groups. The genus Spirula, e. g., as well as the Belemnites, and other congeneric ex- 
tinct Cephalopods with internal chambered shells, are united, solely on account of the 
polythalamous structure of their shell, with Cephalopods of an inferior grade of organ- 
ization, as the Nautilites, while they are separated from those which possess the dibran- 
chiate or higher type of structure,—a type of structure which the laws of coexistence all 
but demonstrate to have been exemplified in the Cephalopods with internal chambered 
shells, first quoted, viz. Spirula and Belemnites. 
The natural affinities of the Cephalopods seem to have been still less regarded in that 
distribution of the species in which the Dibranchiate Decapoda are joined with all those 
Cephalopods possessing chambered shells in one primary division of the class, which 
M. de Haan’ terms Adherentia ; and in which the Dibranchiate Octopoda are raised to 
1 In 1815 this author proposed a binary division of the Cephalopods, which he preferred to term Cryptodi- 
branches, into Cryptodibranches nus and Cryptodibranches testacées.—Journal de Physique, t. Ixxxiii. p. 244. 
2 Monographia Ammoniteorum, &c., 8yo, 1825. 
