366 PALEONTOLOGY OF ILLINOIS. 



GENUS POECILODUS, Ag. 

 P(ECiLODirs CONVOLUTUS, N. and W. 



PI. ii, fig._9. 



TEETH small and thin, spirally enrolled, arched transversely 

 by a strong, obtuse ridge, which occupies the central portion in 

 the line of spiral curvature. On each side of this ridge is a 

 shallow furrow, which, on one side, is bordered by the raised 

 margin of the tooth ; entire triturating surface marked by nu- 

 merous nearly equi-distant ridges or folds, obliquely transverse 

 to the line of enrollment. These rugse are obtuse and, like 

 the inter-spaces, coarsely punctate. 



The analogue of this species is P. angustus, Ag., found in the Garb, limestone 

 of Armagh, Ireland. That species is, however, generally smaller and narrower ; 

 the plications of the enameled surface do not cross the medial ridge affecting 

 only the sulci and they form a ruffled margin to it on either side. In our 

 species they affect equally the ridge and the lateral furrows. 



From the other species found in the Carboniferous strata of Illinois (P. ru- 

 gosus and P. ornatus,) it is distinguished by its smaller size, more convolute 

 form and smoother surface. 



Formation and locality: Keokuk limestone; Warsaw, Illinois. 



GENUS DELTODUS, N. and W. 

 DELTODUS FASCIATUS, N. and W. 



PI. iii, fig. 17. 



TEETH large and strong, sub-spatulate in outline, very 

 obliquely convolute, without longitudinal ridges or furrows; 

 crown surface marked by transverse alternate bands of denser 

 and more porous tissue, which, on the upper portion, are sud- 

 denly bent upward as they approach one side; below are im- 

 perfectly parallel with the rounded margin of the broader end. 

 These bands give a peculiar waved appearance to all the upper 

 surface. 



