op REGS. Say eae Pfc ae MNO, PD 
166 THE CHICAGO ACADEMY OF SCIENCES. 
Shell: Subglobose, solid, umbilicate or imperforate; sur 
face covered with very fine, oblique growth lines which are so 
minute as to be scarcely visible even when viewed with a pow- 
erful glass; the surface is also set with short hairs scattered 
over the whorls; nuclear whorls smooth; periphery rounded; 
sutures well impressed; color yellowish to reddish horn; 
whorls five to five and one-half closely coiled, flatly rounded, 
the last gibbous on the last half and constricted behind the 
peristome; spire somewhat elevated in some specimens, but flat 
in others, convex; aperture narrowly lunate, no teeth or notches 
on the peristome; parietal wall with a long, narrow, more or less 
elevated tooth, which begins near the center of the parietal wall 
and extends generally to the umbilical region in a line parallel 
with the basal reflection of the peristome; peristome white, 
thick, reflected, umbilicus widely open, or wholly imperforate; 
Fic. 26. 
Jaw of POLYGYRA MONODON Rackett. (Original.) 
the region strongly depressed; base of shell rounded, with a 
transverse internal tubercle. 
Greater diameter, 8.50; lesser, 8.00; height, 4.50 mill. (8454.) 
. 4 TAT, Ei it i» P13 6,20 ({B458,) 
yy x B00 32 TM of PTs peters! t Dipab beens (2) o'-1) 
Animal; Witha long, narrow foot truncated before, pointed 
behind; head distinct; tentacles short, cylindrical, thick; eye- 
peduncles long, thick, not much tapering, the black eyes situ- 
ated on large swellings at the tips; color brownish-yellow, al- 
most black on head, neck, tentacles, and eye-peduncles, lighter 
on the foot; respiratory orifice not large. Heart situated be- 
tween the tooth on the parietal wall and the junction of the 
upper part of the peristome with the body-wall. Pulsations 
regular, seventy-one to seventy-six per minute. Length of 
foot 11, width 2 mill. a 
Jaw: Arched, ends blunt, rounded; anterior surface with 
seven stout ribs which denticulate both margins (Fig. 26). 
Radula formula: #+4,9+43+4+4+13+19+3(24—-1—24); 
