156 



In the fossil examples of this genus, a testaceous de- 

 posit or support, apparently the result of successive ac- 

 cumulations, is visible upon the substance to which they 

 are attached, leaving, as it were, the impression of the 

 margin of the shell : as this deposit has never been ob- 

 served on the spot from whence recent specimens have 

 been removed, it may be concluded that the animal in- 

 habiting them seldom, if ever, removes from one spot 

 to another. 



The P. ungarica (commonly called the Fool's-cap 

 Limpet in this country) and its congeners, Sowerby 

 considers more properly to belong to the G. Hipponix 

 of Defrance. See G.Terebratula, No. 15, of the Ge- 

 nera of Shells 



Shells not known to have the support which is observed 

 in many fossil species of this genus. 



Pileopsis ungarica Pileopsis intorta 



mitrula subrufa. 



[And four fossil species.] 



Shells with a known support. 

 [Two fossil species.] 



