149 



PATELLA. 





PATELLA GRANATINA. Linn, 



Mawes Linnctus, 'plate $%,fig. 4, 7. 

 This numerous and beautiful genus of Linnaeus has 

 been subdivided by Lamarck ; from it he has constitu- 

 ted the genera Fissurella, Emarginula, Navicella, Um- 

 brella, Pileopsis, Calyptraea, Crepidula, Parmophora, 

 and Ancylus; each of which possesses sufficiently well- 

 defined characters to authorize a separation, by which 

 they may be more easily distinguished from the still 

 widely extended family of Patellae. As it is now ar- 

 ranged, it comprehends only such shells as are in the 

 form of a wide, concave, and more or less elevated cone, 

 terminated by an imperforated summit. The part of the 

 shell to which the imperforated summit inclines, is the 

 anterior, which circumstance has been clearly estab- 

 lished from the impression of the animal's head being 

 always visible at that part. The posterior end is al- 

 ways wider than the anterior; aperture generally ellip- 

 tical ; the summit of the shell is usually the thickest part; 

 margin without any fissure; the exterior variously mark- 

 ed with striae, longitudinal ribs, granulations, or sharp 

 ridges, rendering the margin angular or waved, though 



