SOME NEW AND RARE CEPHALOPODA. 125 



the rank of an equivalent section, under the name Libera. The primary division of 

 Cephalopods, proposed by M. Deshayes', into the two orders Octopodes and Decapodes, is 

 essentially the same as that of M. De Haan, as the latter group combines the naked 

 or dibranchiate species with the Nautilacea of De Blainville. 



Thus it will be seen that most of the preceding schemes are based on the modifications 

 of the shell or its analogue, and some of them, as that proposed by M. Ferussac, have 

 been published since the modifications of structure in those Cephalopods which inhabit an 

 external chambered shell have been pointed out. It is this circumstance which has 

 chiefly induced me to state here my views of the distribution of the Cephalopods, founded 

 in part on the dissection of the Nautilus Pompilius, and on a comparison of its organ- 

 ization with that of the Cephalopods with internal shells, so far as indications of their 

 structure can be obtained from the hitherto imperfect descriptions of the recent Spirula, 

 and from the remains of the Belemnites. But before I proceed to detail these views I 

 shall briefly adduce the few examples of the classification of the Cephalopods, in which 

 an attempt is made to distribute these highly organized Mollusks into groups founded 

 on considerations of structure of higher importance than tegumentary or testaceous 

 characters. 



The first classification of this nature is due, as might have been expected, to a highly 

 accomplished classical Naturalist, well versed in the zoological writings of Aristotle. 

 This Naturalist, Schneider, to whom we owe the best translation of the ' Historia Ani- 

 malium,' is the first of the moderns who attempted to revive the philosophical views 

 which guided the Father of Natural History in his distribution of the Malakia or Cephalo- 

 pods. For this group of Cephalopods Schneider proposed the name of Octopodia, compre- 

 hending therein the species in which two superadded elongated slender arms are present, 

 but which were distinguished by Aristotle from the ordinary eight arms, under the name 

 of ' Proboscides.' Schneider' divides the class into two groups, which are characterized 

 as follows : — 



1 . Pedes octoni breves, promuscides bince, venter pinnatus, ossiculum dorsi. Ex. Sepia, 

 Loligo, Teuthis, &c. 



2. Pedes octoni longi basi palmati, absque promuscidibus, pinnis et esse dorsali. Ex. Po- 

 lypus, Moschites, Nautilus (or Argonauta) ; and indicates a third, founded on Rumphius's 

 description of the Nautilus Pompilius, with the following character : Pedibus lohatis, seu 

 digitatis absque acetabulis. 



The classification proposed by Dr. Leach', which in one respect is inferior to Schner- 

 der's, is also essentially based on the modifications of the organs of locomotion. In this 

 scheme Dr. Leach leaves entirely out of consideration the chambered shells, and appa- 

 rently restricts the class Cephalopoda to the naked species. These he divides into two 



' Encyclopidie Method. 1830. 



- Sammlung Vermischter Ahhandhngen der Zoologie, &c., 8vo. 1784. 



^ Zoological Miscellany, vol. iii. 1817. 



