364 CALYPTRIDiE. 



young regularly spiral) ; aperture wide, with an internal 

 testaceous appendage. 



Like the animals of Capulida, the members of this 

 family carry and hatch their spawn under the neck, in 

 front of the foot. The simple nature of their pedal disk, 

 and the internal testaceous appendage of the shell, tend 

 to preserve them as a distinct group. The use of the 

 calcareous lamina, which is the first stage in the forma- 

 tion of a columella, is to support the viscera and separate 

 them from the foot or locomotive organ, as the Calyp- 

 tridce have greater powers of locomotion than the Capu- 

 lidcB or the PatellidcB (Owen). 



Genus CALYPTRA, Humphrey. 



Foot large, sub-triangular. 



Shell conical, sub-acuminated, supported upon a solid, 

 calcareous, basal plate ; apex subcentral, a little posterior, 

 with a minute, spiral nucleus ; aperture with the internal 

 appendage half-cup-shaped, open in front, on the posterior 

 side, attached to the apex. 



Syn. Calyptrgea, Lam. Calyptrus, Montf. Calyp- 

 tria, Owen. Mitrularia, Schum. Lithedaphus, Litho- 

 lepas, Owen. 



Ex. C. equestris, Linnmus^ pi. 40, fig. 3, 3, a. 



Calyptra^ like Cochlolepas, is furnished with a cal- 

 careous plate, secreted by the foot, by means of which it 

 is fixed to I'ocks and the under surface of stones, a dis- 

 covery made by Mr. Cuming, who found, on turning over 

 some large stones partly buried in the sand, several living 

 individuals affixed to the under side ; these specimens 

 were described as a new genus by Professor Owen under 



