1888.] 



477 



[Newell. 



subangnlar and slightly concave, while the dorsal is rounded and 

 convex. The septum forming the bottom of the living chamber, 

 and the flattened region of the apertures are strongly inclined 

 toward each other, causing the ventral side of the chamber to be 

 very short. The length from this septum to the lower side of the 

 ventral aperture is but a trifle over one-half the distance from the 



Dorsal view. 



Lateral view. 



Aperture. 



Ventral view. 



septum to the lower part of the dorsal aperture ; also the dorsi- 

 ventral diameter of the shell at this septum equals the latter meas- 

 urement. 



The edges of the aperture are abruptly turned inward leaving 

 a narrow slit connecting the dorsal and ventral openings. From 

 the lateral view this flattened top of the shell is seen to be concave. 

 The slit opens forward into the ventral tube-like aperture which is 



