6 MOLLUSCA. 



Lamarck, and Blainville, may be mentioned as occupying a 

 distinguished place in the anatomical investigation and arrange- 

 ment of Molluscous Animals. Of British writers, the works 

 of Da Costa, Pennant, Montagu, and Donovan may be referred 

 to for descriptions and figures of the British species ; and still 

 more lately Sowerby's Mineral Conchology, and Dr Fleming's 

 British Animals, for details regarding the fossil species. Lis- 

 ter's celebrated collection of plates, first published in 1685, and 

 of which two editions have since been printed, is valuable as a 

 general work. 



In the Regne Animal, Cuvier forms his second great divi- 

 sion of the Animal Kingdom of the Mollusca, under which term 

 he includes the present and the three following classes. The 

 Mollusca he divides into six classes, the Cephalopoda, Pteropo- 

 da, Gasteropoda, Acephala, Brachiopoda, and Cirrhipoda. 



The Mollusca form the twelfth and last class of Lamarck's 

 Histoire Naturelle des Animaux sans Vertebres, in which he 

 follows the ascending series, commencing with the more imper- 

 fectly organized animals. He defines them as follows : 



Soft Inarticulated Animals, furnished anteriorly with a head ; 

 the head more or less prominent, most frequently having eyes 

 or tentacula, or crowned at its summit with arms ; mouth short 

 or elongated, tubular and exsertile, generally armed with hard 

 parts ; mantle various, sometimes with its edges free on the 

 sides of the body, sometimes having its lobes united, so as to 

 form a bag, which partly envelopes the body ; branchiae vari- 

 ous, rarely symmetrical ; circulation double, one particular, the 

 other general ; heart unilocular, sometimes with two divided 

 and widely separated auricles; no gangliar medullary cord, 

 but scattered, and not numerous ganglia, and various nerves ; 

 body sometimes naked externally, and either destitute of solid 

 parts within, or covering a shell or hard bodies, sometimes fur- 

 nished externally with a sheathing or enveloping shell ; shell 

 never composed of two opposite valves united by a hinge. 



Order I. PTEROPODA. No feet to crawl with, or arms to 

 assist their motion or seize their prey. Two opposite and si- 

 milar fins adapted for swimming. 



Order II. GASTEROPODA. Body straight, never in a spiral 

 form, or enveloped in a shell capable of containing the whole 



