SIPHONARIA. 



GENERIC CHARACTini. 



Shell oval or subovate, palelliform ; apex nearer one 

 side and one end, curved in a direction opposite to an angle 

 on the basal edge ; ^vithin, an indentation dividing the 

 muscular impression and extending to the angle of th< 

 lateral edge. 



OBSERVATIONS. 



Adanson was the first to detect the difference between 

 a species of this genus, the S. mouretus, Bl. and Patella 

 which it resembles in general form. He was succeeded 

 by Blainville, but it is to Sowerby that we are indebted 

 for the genus and name which are now adopted. Gray 

 formed a genus for the Gadin of Adanson, which however 

 is referred by other authors to tlie present group ; Adan- 

 son did not describe its animal ; but it is evident from his 

 figure that the two sides of the shell are not symmetrical. 



It resembles Patella, but the shell is distinguished by an 

 unsymmetrical angle on one side, (sometimes obsolete,) 

 denoting the position beneath of the termination of a 

 syphon or respiratory organ of the animal of which the 

 trace remains. On the outer surface, corresponding with 

 this mark, is generally an elevation or rib, extending from 



the summit to the edge, but it is sometimes obsolete^ 



PI. ;3h. 



