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 apertureis 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 bya very thin callus; 
interior of aperture bluish-white or horn colored; umbilicus 
narrow, deep, funnel-shaped. 
° 
Length. Width. Aperture Length. Width, Mills. 
9.50 26.00 9.50 8.00 (8118.) 
8,00 23.00 850 7.50. (8118.) 
9.00 20.00 8.50 5.00 (8116.) 
7.00 18.00 6.50 5.90 (8396.) (distortus.) 
8.50 18.00 7.00 5.50 (8119.) 
8.00 17.00 7,00 6.50 (8119.) 
7.50 21.00 7.00 7.00 (8117.) 
8.00 22.00 8.00 7.00 (8117.) 
8.50 17.00 7.00 6.50 (8389.) 
4,50 5.50, 4,25 2.00 (8782.). 1 Age 
6.50 7.00 6.00 2.50 (8782.) \ develop- 
1.25 12.00 7.00 4.50 (8732,) | ment. 
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 11.00 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: 32%,+4+4+4+34% (t9—1—1I9); central 
tooth witha base of ea aaa vent longer ened 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 
