PLEUROCERA. 57 



only of four specimens received is full grown. This has, above 

 the angle of the last -whorl, a few undefined tubercles. Below this 

 angle there are five or six well defined transverse striaj. None of 

 the specimens have bauds. Should adults generally be 

 found with tubercles, then this species should be placed 

 in the tuberculate group and not in the smooth one, where 

 I have now placed it in the above description. The aper- 

 ture is nearly one-third the length of the shell. I have 

 great pleasure in dedicating the species to Dr. Spillmau, 

 who has done so much for the natural historj^ of his own 

 and other Southern States. 



The typical excuratum differs widely enough from 

 undulatum, Say, but there exist intermediate forms of a nature 

 to perplex the naturalist. Among these may be mentioned P. 

 ponderoswn, Auth. {dux, Lea), with the tubercles and canal 

 nearly obsolete and the revolving strioe very faint, so that the 

 surface of the shell appears at first sight flat and smooth ; also 

 annidiferum, Conr., in which the revolving lines are more 

 strongly developed. These shells all partake of one general 

 tj^pe and form a natural group of closely related species, at 

 the least. 



5. P. moniliferum, Lea. 



Trypanostoma moniliferum. Lea, Proc. Acad. Nat. Sci., p. 172, 18G3. Jour. Acad. 



Nat. Sci., Y, pt. 3, p. 295. t. 30, f. 125, March, 18G3. Obs.. ix, p. 117. 

 lo nodosa, Lea, Proc. Acad. Nat. Sci., p. 393, 18GI. Jour. Acad. Nat. Sci., v, pt. 3, p. 



340, t. 39, f. 212, March, 1803, Obs., ix, p. 108. 

 lo variahiUs, LEA, Proc. Acad. Nat. Sci., p. 393, 18G1. Jour. Acad. Nat. Sci., v, pt- 



3, p. 347, t. 39, f. 2U, March, 1803. Obs., ix, p. 109. 



Description. — Shell tuberculate, thick, pyramidal, yellowish or 

 greenish, banded or without bands; spire high, pyramidal; sutures 

 irregularly impressed ; whorls about ten, flattened, striate below, 

 sometimes obscurely sulcate, tuberculate on the periphery ; aperture 

 rather large, rhomboidal, within either white or salmon and gencrallj- 

 double-banded ; outer lip acute, very sinuous ; columella thickened 

 below and very much twisted. 



Operadum ovate, very dark brown, with the polar point near the 

 base. 



Habitat. — Tennessee; Prof. Troost and Mr. Anthony: Florence, 

 Alabama; Rev. G. "White, Mr. Pybas and Mr. Thornton: Cumberland 

 Eivcr; Dr. Powell: Ohio Kiver, near the mouth in Illinois; J. Ronald- 



