478 CHITOA'IN^. 



Shell with the valves external, narrow, elongate, sub- 

 cordate ; the hinder valve large, with the apex posterior, 

 and with a deep notch on its hind lower edge. 



Ex. S. incisus, Sowerhy, pi. 54, fig. 6, 6, a. 



The plates of insertion are nearly the same in this 

 genus as in Chiton, that of the terminal valves being few- 

 lobed, that of the posterior deeply fissured, and that of 

 the middle tri-lobed ; the fissured mantle-margin is the 

 most obvious external character. Two species only, from 

 the Philippines, are known. 



Species of Schizochiton. 

 elongatus, Reeve. incisus, Sow. 



Genus MOPALIA, Gray. 



Mantle-margin moderately wide, bristly or hairy, with a 

 sinuosity on the hinder lower edge. 



Shell with the valves almost external, broad, transverse, 

 slightly covered at the sides by the mantle ; the hinder 

 valve large, with the apex sub-central, and posteriorly 

 slightly sinuated. 



Ex. M. Hindsii, Sowerhy, pi. 54, fig. 7. 



In this genus the plate of insertion of all the valves 

 has only a single notch on each side. The front edge of 

 the mantle is sometimes greatly dilated, and a small por- 

 tion of the lateral areas of the valves of the shell is 

 covered by the mantle. 



Species oj Mojmlia. 



asperrima, Couth. ciliala, Sow. 



Blainvillii, Brod. Hindsii, Sow. 



