THE NATURAL HISTORY SURVEY. 145 
rounded; suturesimpressed; whorls, five and one-half, convex, 
closely coiled, the last deflected above the aperture and con- 
stricted behind the peristome; spire depressed, a little convex; 
aperture lunate, lobed by the teeth on the peristome; the tooth 
on the upper part of the outer lip is broad and low, placed 
squarely on the peripheral portion of the lip; the one on the 
basal portion of the lip is small and tubercular; the parietal 
tooth is of good size, elevated, narrow, oblique, and extends 
from the upper part of the parietal wall almost to the basal ter- 
mination of the peristome; the parietal tooth is directed toa 
point between the two teeth on the outer lip; peristome reflected, 
Fig. 16. 
Apertures of PoLyGyra. (After Pilsbry.) A, TRIDENTATA Say; B, 
FRAUDULENTA. Pilsbry. 
white, thickened, sometimes grooved; umbilicus widely open, 
exhibiting all the volutions; base of shell convex (Fig. 16, A). 
Greater diam., 15.00; lesser, 15.00; height, 7.00; umbilicus, 2.75 mill. (8447.) 
Animal: As usual in the genus; color yellowish-white on 
foot, darker on sides of body and neck, and jet black on eye- 
peduncles and tentacles; mantle collar yellowish; the foot is 
not very long and is rather wide, and the lateral expansions 
are very pronounced; posteriorly it terminates rather acutely 
and anteriorly it is truncated; the animal appears much too 
small! for the shell. The foot measures about 20 mill. in length 
and about 4 mill. in width when the animalisin motion. Heart 
pulsations regular, eighty-five to ninety per minute. Whenthe 
animal was partly retracted within its shell the heart beat thirty- 
three to fifty-five times per minute. 
Faw. Arched, low, wide, ends blunt; anterior surface 
with eleven ribs which denticulate both margins. 
Radula formula: %$+149+4+19+14) (25—1—25). Central 
tooth with a rather wide base of attachment, the’ lower outer 
corners expanded and the lower margin excavated; reflection 
tricuspid, the center cusp long, reaching to the lower border 
