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, T T ; intermediate, 6; middle lateral, 18; outer lateral 

 smooth (o). (Vide Stimpson.) 



Distribution: Europe and America. 



138. Paludestrina nickliniana Lea, 1839. PI. xxvi, fig. 11. 



Paludina nickliniana LEA, Trans. Amer. Phil. Soc., VI, p. 92, pi. xxiii, 



fig. 109, 1839. 

 Amnicola attenuata^ HALDEMAN, Monograph, pt. 4, p. 3 of wrapper, 



pi. i, fig. 13, 1844. (Variety.) 



FIG. 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.) 

 4.50; " 2.00; " " 1.50; " 1.25 " (9691.) 



4.25; " 2.00; " " 1.25; " 1.00 " 



