THE NATURAL HISTORY SURVEY. 289 



are rounded and have very deep sutures between them; aper- 

 ture broadly lunate, somewhat expanded below, and with a 

 v-shaped angle above; the aperture is exactly the height of the 

 body-whorl; peristome acute, thin, rounded, a little thickened 

 on the inside and bordered within by a wide chocolate or yel- 

 lowish band extending from one termination to the other; ter- 

 minations approaching and connected by a very thin callus; 

 interior of aperture bluish-white or horn colored; umbilicus 

 narrow, deep, funnel-shaped. 



Animal: Dark brown, sometimes dotted with yellowish; 

 foot short, wide, rounded before and behind; tentacles long, 

 filiform, always in motion; head not separated from the rest of 

 the body by a constriction; eyes situated on prominences at 

 the inner base of the tentacles. Length of foot, 13.00, width 

 4.50 mill.; tentacles I i.oo mill, in length. Mantle margin sim- 

 ple. Heart pulsations seventy to seventy-four, very regular. 



Jaw: With a median arcuated, crenulated plate and two 

 narrow accessory plates. 



Radula formula: ^-V+l+l+t+^-V 09- 1-19); central 

 tooth with a base of attachment longer than wide, swollen and 

 rounded on the lower half; reflection bicuspid, broad, the cusps 

 long and narrow, fang-like; lateral teeth with a quadrate base 

 of attachment and a large, square reflection which is tricuspid, 

 the center cusp being very wide and blunt and the side cusps 

 long and narrow; intermediate teeth similar to laterals, but 

 varying in the number and arrangement of the cusps; some- 

 times the change from laterals to marginals is abrupt, at others 

 it is very gradual, and in some membranes there appear to be 

 no two marginals alike; the large, blunt, central cusp in the lat- 

 eral teeth becomes a long and narrow cusp in the intermediate 



