158 



now alluded to had five distinct laminae in one ex- 

 ample, and six in the other, 



Calyptraea extinctorium Calyptraea equestris 

 laevigata tectum-sinense. 



CREPIDULA. 



PATELLA FORNICATA. Linn. 



Mawes Linnceus, plate 32, fig. 3. 

 This is another very distinctly marked separation from 

 the G. Patella. Shell oval or oblong, a much depressed 

 concave exterior; the spire inclined obliquely to one 

 side; margin entire, and the opening partially closed 

 horizontally by a partition, giving it the appearance of 

 a half-decked boat: some have angular longitudinal 

 ribs on the surface, others have them armed with spines 

 or prickles; they, like the generality of shells blended 

 by Linnaeus with the G. Patella, seem constantly fixed 

 to one spot, as the shape of their base is conformable 

 to the substance on which they adhere. They never 

 have an operculum, which distinguishes them from the 

 G. Navicella. 



