184 THE CHICAGO ACADEMY OF SCIENCES. 
by very fine, oblique, crowded growth lines, which disappear 
on the large, rounded, flat nucleus; color light yellowish-horn; 
periphery rounded; sutures deeply impressed; whorls six, nar- 
row, rounded, very regularly increasing; spire generally ele- 
vated, sometimes a little depressed, convex; aperture trans- 
verse, wider than high, somewhat moon-shaped in some speci- 
mens, contracted by the body-whorl; peristome thin, acute, 
simple, the terminations widely separated; umbilical region 
indented, but the umbilicus closed or minutely perforated; base 
rounded; last whorl angular in front, the angularity becoming 
obsolete on the latter part of the whorl. 
Greater diameter, 2.25; lesser, 2.00; height, 1.75 mill. (10648.) 
gS «s 2.95: AB iC Al DOGS) 
* es 2.90; © BOSS BADR 4 Cree. 
“ © 3.00; « 250; ~~ 250. ©" (12295) 
% * 3.00; BRD 2a AGelS lene 
Animal; With a long and narrow foot, with distinct cau- 
dal mucus pore and pedal grooves; tentacles short and blunt; 
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FIG, 39, 
Teeth of EucoNuLUS FULVUS Drap. (Original.) c, central tooth; 
1, first lateral; 15, fifth perfect marginal; J, jaw. 
eye-peduncles long and tapering; color blackish on head, neck 
and eye-peduncles, rest of body dirty white; a black stripe 
extends from each eye-peduncle over the back to the shell. 
When viewed dorsally the animal is almost hidden by the shell, 
which is large in comparison with the foot. Heart situated 
near the umbilical region, pulsations variable, ranging from 
one hundred and thirty-five to one hundred and fifty per minute. 
As in all mollusks, warmth accelerates the action of the heart. 
A specimen measuring 4 mill. in length was almost jet black 
in color. 
Jaw: Strongly arched, very wide in the middle and taper- 
ing at either end, which is rather pointed; margins smooth, no 
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