548 HISTORY OF SYSTEMS. 



merely sentient or instineted animals of Lamarck, and em- 

 brace the mollnscous and the conchiferons classes, which he 

 proposes to call mantled animals — animalia penulata. The 

 Molluscan race are divisible into two branches, the phanero- 

 gamous and the agamous or cryptogamic. The first copu- 

 late ; the second have the sexual character masked and fecun- 

 date themselves. The phanerogamous are either finned or 

 finless. There are two classes of the finned section, the 

 CEPHALoroDS and Pteropods ; and the finless are all Gas- 



TEROPODS. 



The Cephalopods divide themselves into two orders. 1. 

 the Decapods, with two families, one embracing the multilo- 

 cular shells, and hence named Polythalaraa ; the other named 

 Enterostea, and represented by the genera Sepia and Loligo. 

 The second order or Octopods has also two families, — a shel- 

 less one (Acochlides) for the Octopus ; and one with its fine 

 unilocular shell (Cymbicochlides), to receive the Ocythoe, 

 Argonauta, and Bellerophon. 



The class Pteropoda has two orders, Megapterifgia and 

 Microptenjgia. In the first the swimmers are large. One 

 family of them has a distinct head (Procephala), as instanced 

 in Limacina and Clio ; the other (Cryptocephala) has the 

 head inconspicuous, with branchiae separate from the swim- 

 mers ; and the genus Hyala?a alone represents it. The se- 

 cond order has small swinnners, and the body has no shell ; 

 and a single genus, Pneumodermon, makes evident its insig- 

 nificance. 



The Gasteropoda are either hermaphroditical or dioe- 

 cious ; and in both sections there are branchiferous and pul- 

 monated mollusca. The order Nudibranchia introduces the 

 first series, which seems to be connected with the Pteropods 

 by the genus Carinaria, the first of the Nudibranches. These 

 have three families named, from the position and form of the 

 respiratory organs, Urobranchia, Seribranchia, and Phyllo- 

 branchia. This order is followed by that of the lufero- 

 Iwanchia, and this again by the Tectihranchia, of which one 

 family (Tentaculata) has, and the other (Accra) has no tenta- 

 cula. The order Puhnonea succeeds, and these are either 

 naked (Nndilimaces), or terrestrial and cochleated (Geococh- 

 lides), or aquatic and shelled (Limnocochlides.) 



There are only two orders of dioecious Gasteropods, The 

 Pne^imopoma, or operculated terrestrial mollusca, embraces 

 the family Helicinides and Turbicina, each represented by a 

 single genus. The Pecthiihrancliia is, on the contrary, a very 

 extensive order with not less than eighteen families, divided 

 into two very unequal sections according as the shell is ex- 



