322 THE CHICAGO ACADEMY OF SCIENCES. 
tinct, but there is a total absence of copulatory organ in the 
male. In the present species there is a peculiar sinus in the 
female, on the right side of the foot, between the operculiger- 
ous lobe and tentacle; the male is without this sinus. The 
only way to be absolutely sure of the sexes is to crush the 
body and examine with a microscope, when, if a male, sperma- 
tozoa will be found, and, if a female, ova will be found. 
Distribution: New York to Great Lakes, south to Ohio 
River drainage. 
Geological distribution: Pleistocene. 
Habitat: Found generally on a sandy or rocky bottom in 
shallow water, where there is little or no current. 
Remarks: This species is subject to no little variation in 
its obesity and ornamentation; the typical form is almost 
smooth but the variety zwfensum is more strongly keeled on the 
periphery and has several additional spiral lines. It is sepa- 
rated from P. e/evatum by its more rounded whorls, particularly 
the last, and by its aperture, which is oval instead of triangu- 
lar. The animal is slow and very sluggish in movement, and 
in an aquarium spends most of the time on the bottom of the 
tank, with its body half protruding from its shell and with its 
rostrum and tentacles slowly moving about. The species 
seems to be confined to the southern region and has thus far 
been found only in Wolf Lake. 
130a. Pleurocera subulare intensum Anthony, pl. xxxyv, fig. 3. 
Melania intensum ANTHONY, REEVE, Monog. sp. 371. 
Shell: Differing from the typical form in being of a much 
darker greenish-horn color, and in having the carina above the 
suture extending in a more prominent manner to the base of 
the last whorl. There are also seven subobsolete spiral lines, 
especially on the base, which are not developed in sudbulare. 
Length, 24.00; width, 8.00; aperture length, 7.00; width, 4.50 mill. (8735.) 
Antmal, Dentition, etc.: As in subulare. 
Distribution and Habitat: As in subulare. (?) 
Remarks: The variety does not seem to be as common as 
the typical form and has been found only in the, Desplaines 
River. It approaches e/evatum in form, particularly when there 
is a decided keel on the periphery. 
131. Pleurocera elevatum Say, p). xxxv, fig. 4. 
Melania elevata SAY, Journ. Phil. Acad., Vol. II, p. 176, 1821. 
Melania tracta ANTHONY, Proc. Bost. Soc. Nat. Hist., Vol. III, p. 361, 
1850. 
