I 



SIPHONARIA, 



very narrow line, over which lies the head of the animal: 

 the extremities of the muscular impression are rather 

 expanded, particularly that immediately hehind the canal. 

 The canal itself sometimes forms a distinct groove within 

 the shell, running from the vertex to the margin, and a' 

 corresponding prominence may he observed on the out- 

 side, forming a ridge from the vertex to the margin : hut 

 the internal groove and the external ridge are not always 

 distinct ; the place of the head and that of the canal can, 

 however, be easily distinguished in all cases. 



We are acquainted with seven or eight species of this 

 Genus, all of which are recent, and marine ; we. have 

 them from Brazil, the West Indies, Senegal and Tristan 

 d'Acunha. 



In our plate are represented. 



Fig. 1. Siphnnaria Sipho. 



2. concinna. 



3. Tristensis. Patella Tristensis, Leach, 



4. exigua. Lepas exigua, Martini, 



