354 THE CHICAGO ACADEMY OF SCIENCES. 
The number of denticles on the cusps varies in different 
species as follows: central, 7-18; intermediate, 7-12; inner 
lateral, 5-10; outer lateral, 5—16. 
146. Vivipara contectoides W. G. Binney, pl. xxxvi, figs. 1, 2, 3. 
Limnea vivipara SAY, Nich. Encycl., Amer. ed., pl. ii, fig. 5, 1817. 
(Paludina of later editions.) 
Vivipara contectoides W.G. BINNEY, L. and Fr. W. Sh., Part III, p. 28, 
figs. 41-44, 1865. 
Shell: Rather thin, rounded, swollen; color greenish- 
horn, either plain or with four revolving brown bands, of 
which three are on the body of the whorl and one on the base, 
the upper whorls showing but two bands; surface shining, 
smooth, lines of growth numerous, fine, crowded, a trifle ob- 
lique; surface broken in one or: more places by the mark of 
the former peristome, which leaves a black line; spire rather 
short, subconic; apex small, knob-shaped, elevated; sutures 
very deeply impressed; whorls five, regularly increasing in 
size, swollen; aperture nearly circular, oblique, entire, the in- 
ner wall of the aperture being placed against the body-whorl, 
bluish-white inside, showing the four bands through the shell; 
peristome entire, thin, sharp, bordered with black, reflected 
near the umbilicus; base of shell rounded; umbilicus narrow, 
deep, in some examples almost covered by the reflection of 
the peristome. 
Length, 28.00; width, 21.00; aperture REE 14.50; width, 11.50 mill. (8840.) 
“80,00; “« 24.00; « 16.00; “ 13.00 “ (8845.) 
“81.00; “ 26.00; - “ © 15.00; “12.50 «  (884h) 
“38.00: 25.00; “16.00; “ 13.00 “ (9180.) 
Animal: With a short and very wide foot, expanded lat- 
erally before and rounded behind; tentacles short and trian- 
gular, the eyes situated on prominences on their outer sides; 
color dark brown with lighter patches here and there; rostrum 
short and thick, cylindrical, blunt; there is a short siphon on 
the right side and a small lappet on the left side; operculum 
concentric, horny, rather thin, concave, the nucleus a little 
below the center of left side (Pl. xxxvi, Fig. 2); operculigerous 
lobe on right side of body, near the center of the hinder end 
of the dorsal surface of the foot. Length of foot, 22.00; width, 
14.00 mill. In the male contectérdes the right tentacle is pro- 
duced into a thick, cylindrical, copulatory organ, or verge, 
with a small hook at the end. 
Radula formula: 4+4+4+4+44+4-4++4 (3-1-3); central 
