42 MOLLUSCA. 



species of the genus Lepas of Linnaeus. The shells belong- 

 ing to the Linnaean genera Sarpula and Dentalium, are 

 transferred to the class termed Annelides. 



This system of the molluscous animals is unquestionably 

 the most perfect of all those which have been published. 

 But, with all its excellence, we must inform the reader, 

 that many species, nay, whole genera, have their places as- 

 signed them in this natural method, merely because the 

 shells occupied a similar position in the artificial system, the 

 form of the inhabitants being unknown. 



SECTION IV. Mixed Systems. 



In this section, we shall confine our remarks to the only 

 system of this kind of any consequence which has hitherto 

 appeared, and which is the production of the late industrious 

 Lamark, one of the most celebrated zoologists of the French 

 school. The Systems des Animaux sans Vertebres, Paris, 

 1801, of this author, embraces the whole range of animals in- 

 cluded in the classes Insecta and Vermes of Linna3iis. Where 

 treating of the Mollusca he divides them into two orders. 

 The first, termed Cephalous, from possessing a head, in- 

 cludes the univalves. The second, termed Acephalous, from 

 the absence of a head, includes the bivalves. This eminent 

 author greatly modified his views, as appears from what he 

 announced in his Extraitdu Cours de Zooloyie, Paris, 1812, 

 the prelude to his last and great work, Histoire Naturelle 

 des Animaux sans Vertebres, the fifth, sixth, and seventh vo- 

 lumes of which refer to the Mollusca, he fortunately lived to 

 finish between the years 1818 and 1 822. The arrangement 

 adopted in this invaluable work, has been greatly admired, 

 a circumstance which induces us to give the following sy- 

 noptical view of its contents. 



