2 SYSTEMATIC DISTRIBUTION. 



lary masses distributed to different parts of the 

 body; one of the masses being placed over the 

 gullet, and enveloping it like a collar. 



Linnasus refers all the animals inhabiting shells to 

 five different genera ; viz., Limnx, Ascidia, Anomia, 

 Clio, and Sepia. These genera may be regarded 

 as the types of the classes proposed by Cuvier. 

 Poll had, before his time, considered three of them 

 as orders, under the names of Mollusca Reptantia, 

 Suhsilentia, and Bracltiata. 



This division of the animal kingdom is subdivided 

 into five classes in the following manner : — 



A. Crawling on a foot placed under the body. — 

 Pedif era. 

 I. Gasteropoda, Gasteropods, or Univalves, 

 which have a distinct head, furnished with 

 eyes and tentacles, and are usually protected 

 by a conical more or less spiral shell, often 

 furnished Avith an operculum. 



II. CONCIIIFERA, Conchifers, or Bivalves. — 

 Having the mouth placed between the gills, 

 they and the body enclosed between the two 

 leaves of the mantle, which are covered with 

 two shelly valves united above by a ligament. 



B. Destitute of any foot. — A p o d a. 



III. Brachiopoda, Brachiopods, or Lamp Shells. 

 — Having the mouth placed at the base of 

 two spirally twisted ciliated arms, between 

 the two leaves of the mantle, which are co- 



