244 ON THE CLASSES OF THE 



would thus be necessarily free from all such frauds as 

 those of Giseni, who so long imposed on them as a new 

 genus of Multivalves, under the appellations of Tricla 

 and Gimiia, the apparatus which incloses the stomach of 

 the Accra. 



It will perhaps be noticed by the reader, that if I have 

 hitherto aimed little at a general arrangement of the Mol- 

 lusca, there has been a still weaker attempt made at any 

 accurate designation of the classes into which these may be 

 grouped. Nay, perfectly satisfied if it should be in my 

 power to prevent the appearance of any great chasm in 

 the route chalked out for myself, I have always adopted 

 the divisions of M. Cuvier, since it must be obvious that 

 a person is much less likely to be wrong in agreeing with 

 this great anatomist, than in hazarding new speculations 

 without sufficient knowledge of the subject to support 

 them. Lamarck, however, has separated the Acephala of 

 Cuvier from the Mollusca, under the name of Conchifera ; 

 though, as he rests the importance of this division upon 

 points which are certainly of very secondary consideration, 

 and which he himself acknowledges to shade gradually into 

 the construction of his Mollusca, we can have no hesita- 

 tion in pronouncing the alteration to be artificial. It is 

 plainly a mistake which has arisen from his paying too 

 much attention to the manner in which the hinges of bi- 

 valve shells are articulated, and too little to the observa- 

 tions of Cuvier and Poli, on the internal anatomy of the 

 animals themselves. On descending into subdivisions, I 

 am nevertheless inclined to believe the distinction which 

 he institutes between the Dimyaria and Monomyaria, as 

 two groups of Conchifera, to be excellent, and apparently 

 much better than his great division of Cuvier's Gasteropoda. 



