338 THE CHICAGO ACADEMY OF SCIENCES. 
with a long process extending laterally from the base, which 
is also provided with a central cavity and a projection on the 
inner side of the base, the reflected cusp with six denticula- 
tions; the inner lateral has a long projection or shank to the 
base, which is greatly thickened on the outer margin, and the 
reflected cusp is twelve-denticulate; outer lateral very long 
and narrow, arcuate, apparently very finely denticulate on the 
summit (when magnified seven hundred diameters.) With 
low powers it is apparently smooth. Troschel found the for- 
mula of B. thermalis, a European form, to be as follows: rha- 
chidian, ;2;; intermediate, 6; middle lateral, 18; outer lateral 
smooth (0). (Vide Stimpson.) 
Distribution: Europe and America. 
138. Paludestrina nickliniana Lea, 1839. Pl. xxvi, fig. 11. 
Paludina nickliniana LEA, Trans. Amer. Phil. Soc., VI, p. 92, pl. xxiii, 
fig. 109, 1839. 
Amnicola attenuata, HALDEMAN, Monograph, pt. 4, p. 3 of wrapper, 
pl. i, fig. 18, 1844. (Variety.) 
AX 
Fie, 122. 
Radula of PALUDESTRINA NICKLINIANA Lea, (After Stimpson.) C, 
central tooth; 1, intermediate tooth; 2, 3, lateral teeth. 
Shell: Elongately ovate, turreted; color greenish-horn; 
surface shining, lines of growth numerous, crowded, raised so 
as to roughen the surface of the shell; sutures deeply im- 
pressed; whorls four to four and one-half, very convex; spire 
elevated, rather sharply conical; apex small, round, almost 
concealed in the volution of the second whorl; aperture roundly 
ovate; peristome sharp, a little thickened on the inside, con- 
tinuous, the columellar lip being covered with a raised callus 
which connects the terminations; base of shell rounded; um- 
bilical region rimate and indented. 
Length, 4.00; width, 2.00; aperture length, 1.25; width, 1.10 mill. (9690.) 
ea 4.50 5° ee iQ: a as Loss YT 1 (9691.) 
“ 4,25; “ 2.00; Ty “ 1.25: “ 1.00 “ (9691.) 
