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, Sepice- 

 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. Ferussac in 

 the great work still in progress of pubhcation 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 Acetabuliferes ; all those having siphonated chambered shells form a second 

 order, termed Siphoniferes ; and the non-siphonated 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 dihran- 

 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. Spirida 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 Adharentia ; and in which the Dibranchiate Octopoda are raised to 



' In 1815 this author proposed a binary division of the CepJmlopods, which he preferred to term Cryptodi- 

 branches, into Cryptodibranches nus and Cryptodibranches testace'es. — Journal de Physique, t. Ixxxiii. p. 244. 

 - Monographia Ammoniteorum, &c., 8vo, 1825. 



