MOLLUSCA, 



BY 



DR. F. H. TROSCHEL. 



OF works having for their professed object the giving of 

 accurate figures of all the species of Conchylia at present 

 known, there are four in progress ; and it appears from 

 them that both authors and publishers concur in zealously 

 striving to do their utmost. It is to be regretted that these 

 works are of necessity so extensive as almost to preclude 

 the possibility of their coming within the means of the 

 private student ; and since each of them professes to give 

 figures of every species, it is evident that when completed 

 they will be in great measure repetitions of each other. 



The number of species has latterly become enormous, 

 and when the number of species of a genus is increased by 

 a writer, four- or even six-fold, we may, probably, be allowed 

 to doubt whether he is justified in so doing ; and it is certain 

 that many species will be united as varieties under a single 

 one when the same materials fall into the hands of another 

 inquirer. I of course refrain from any criticism of these rich 

 materials. The four works to which I have thus equally 

 alluded are the following : 



Illustrations conchyliologiques, ou Description et Figures 

 de toutes les coquilles connues vivantes et fossiles, classees 

 suivant le systeme de Lamarck, &c., par Chenu. Livr. 1, 2, 

 Fol. Paris, 1843. 



Lovell Reeve, Conchologia iconica. A complete Reper- 

 tory of species, pictorial and descriptive, Nos. 1, 2. Lon- 



