100 MOLLUSCA. 



19. CONUS. Tliis genus is so very natural, that it has 

 undergone no changes since the days of Linnaeus, except by 

 the addition of new species. That author was acquainted 

 with thirty-five species and a few varieties ; but M. Hawss 

 communicated to Bruguiere descriptions of one hundred and 

 forty-six, from specimens existing in his own cabinet. We 

 cannot boast of any British species. 



20. CYPRJEA. This genus is equally natural as the for- 

 mer. It has undergone no change since the days of Major. 



21. BULLA. This genus presents to the mere conchologist 

 a source of great perplexity. It displays at once the absurdity 

 of dividing the molluscous'animals in to testaceous and naked, 

 since no such distinction is observable in nature. Many of 

 the shells which were formerly included in this genus are 

 found to be contained w r ithin the common integuments of 

 the animal. It was this circumstance which induced Lin- 

 naeus to separate the limax and the aplysiafrom the vermes 

 testacea. Both of these have shells, but they are concealed. 

 In imitation of the same principle, Lamark has formed a new 

 genus among the naked mollusca, called BULLJEA, for the 

 reception of those bullae in which the shell is concealed. 

 The bulla aperta is the type of the genus. The bulla plu- 

 mula of Montagu is another shell included in the animal, 

 which is very closely connected with the genus Pleuro- 

 branchia of Cuvier. (Annales du Mus. v, 269). It may be 

 asked, are all the other bullae found in similar situations, and 

 consequently do they belong to the naked mollusca ? La- 

 mark considers, and apparently with reason, that all those 

 which are distinctly spirally involuted, and ornamented with 

 colours, are not entirely inclosed in the cloak of the animal, 

 and ought therefore to be ranged with the testaceous mol- 

 lusca. How few British species does this character include. 



