30 MOLLUSCA. 



cavity ; in several species it contains a small, flat, and oblong shell, 

 or at least a calcareous concretion in place of it. The respiratory 



Shell having- no plaits on the 

 I columella, the edges of the 



J aperture united circularly. 

 I Animal a vermicular Tra- 

 I ch^lipode, and breathing wa- 

 ^ ter only, 



r Shell turretted or conoid, aper- 

 I ture round or oblong, not 

 1 widened, having the edges 



■^ disunited : they appear fur- 

 j' nished with an operculum. 

 The animal breathes only 

 L water. 



Genus Cerithium . . 



. Pleuromata . 



. Turbinella . , 



. Cancellaria . 



. Fasciolaria . , 



. Fusns 



. Pyrula 



Struthiolaria 

 Ranella . . . . 



Murex 



Triton 



Rostellaria 

 Pterocera. . 

 Strombus.. 



First Division. — ' 

 Species without 

 any permanent 

 varix or thick- 

 ened lip on the 

 right margin. 



Second Di\'ision. 

 — AJl the species 

 having perma- 

 nent varices, or 

 a thickened lip 

 on the right side. _ 



>1 



Second Section. — Les Zoophages. 

 Animals feeding on animal substances only. 



"Trach^lipodos with a project- 

 ing or salient syphon, breath- 

 ing water only, conveyed to 

 the branchiae or gills by that 

 syphon ; they feed upon ani- 

 mal substances only, are 

 marine, without jaws, and 

 provided with a retractile 

 proboscis. Shell spirivalve, 

 inclosing the animal; the 

 aperture either caualiculated 

 or notched at the base ; the 

 right lip not changing its 

 form by age, the can.il more 

 or less long ; all having oper- 

 cula. In the first division of 

 this family, the additional 

 growth is but slightly marked, 

 in the second, it is distin- 

 guished by thickened bands 

 or varices, which remain on 

 the external whorls, except 

 in the genus Struthiolaria, 

 which has only a thickened 

 lip. 

 '"Shell having a canal more or 

 less long at the base of the 

 aperture, the right side of 

 which changes its form with 

 age, and becomes Aving- 

 shaped ; a sinus at the lower 

 part of the lip. These shells 

 present the remarkable fact 

 of being totally different in 

 form in an adult state, from 

 that in the young ; a fact 

 only observable in the G. Cy- 

 prsea besides this family. 

 The operculum of the ani- 

 mals of this family is homy, 

 long, and straight. 



Second Family. 

 Les Ail^es. 



