378 PALAEONTOLOGY OF ILLINOIS. 



" Loxonema rugosa, M. and W. 



PI. 31, figs. 11 a, lib, lie. 



Loxonema rugosa, Meek and Worthen, October, 1860. Proceedings Acad. Nat. Sci., 

 Philad., p. 465. 



Shell small, elongate-conical ; volutions seven and a half to 

 eight, very slightly convex, increasing gradually in size, last 

 one rather abruptly rounded in the middle, not extended below ; 

 suture moderately impressed; aperture obliquely ovate. Sur- 

 face of each whorl ornamented by about eighteen straight, dis- 

 tinct, rounded vertical folds or costse, which equal the depres- 

 sions between, and are disposed so as to range in regular lines 

 from the body whorl to the summit of the spire ; those on the 

 last whorl becoming abruptly obsolete below the middle. No 

 lines of growth visible. Length, 0.44 inch; breadth, 0.18 

 inch; length of aperture, 0.12 inch; breadth of do., 0.08 inch. 

 Apical angle convex, divergence 25 °. 



This shell is very nearly like the last, but differs in being less attenuate 

 towards the summit of the spire, and in having its costse arranged in regular 

 rows up the spire, while those of the last are usually arranged so as to alternate 

 on the different turns. Its costae are also proportionally a little smaller, and 

 somewhat more closely arranged. Notwithstanding these differences, however, 

 more careful comparisons of other specimens examined since we first published 

 a description of this form, lead us to suspect that it may possibly prove to be 

 only a variety of the last, though we have not been able to fully satisfy our- 

 selves that this is the case. 



The lip of our specimen being broken, our figure does not show the form of 

 the aperture, which must have been more rounded than the specimen figured 

 would indicate. 



Locality and position : Springfield, 111.; Upper Coal Measures. 



Loxonema multicostata, M. and W. 



PI. 31, fig. 12 a, 12 6, 12 c. 



Shell small, conical; spire moderately elevated; volutions 

 about seven and a half, somewhat convex, increasing gradually 



