1S70.] ^^"^ [Iliiytleu. 



are broken away in the specimen before me; they are strongly compressed, 

 smooth, with sharp, beantifnlly annulated cntting edges, unequally di- 

 vergent; left one — viewed from before — most inclined from a vertical line 

 and broadest at base; transverse section of both lenticular. 



In the collection of the State Geological Survey there is a tooth from 

 the Upper Coal Measures of southwestern Iowa, which is doubtless spe- 

 cifically identical with the Nebraska specimen, though possessing some 

 slight differences. In the Iowa specimen the base has, as in the above 

 described tooth, a lozenge-shaped outline, its posterior extremity is more 

 abruptly truncated, and the pad-hke elevation surmounting its surface is 

 ellipitical with its longer axis transverse to the root — in other respects the 

 same as the Nebraska tooth; viewed in front, the right lateral cone is the 

 strongest and most inclined laterally, and the bases on the anterior face 

 are swelled out, producing an angular ridge or buttress, which, however, 

 is lost both in the crown above and in the root below. These two individ- 

 uals are the only ones I have had opportunity to examine, and comparing 

 them with the excellent description and figures of D. latus, Newb., I can- 

 not doubt but that they are distinct from that species. The present spe- 

 cies is described from the Coal Measures of Ohio and southwestern 

 Indiana, the latter locality holding a stratigraphical position probably be- 

 low the Nebraska horizon. 



Form, and Log. — Upper Coal Measures. 



Genus PETALODUS, Agassiz.- 

 Petalodus destkuctoe, N. and W. 



Eeference. — Newberry and Worthen, Geol. Illinois, Vol. II, p. 35; PI. 

 II, figs. 1-3. 



The collection contains a large, almost perfect specimen of the above 

 species, which presents the following characters: 



Description. — The crown is sharp, compressed, gradually thickening 

 toward the base ; crest more or less gently arched from the lateral extremi- 

 ties, obtusely acuminate at the apex, and distinctly striated for the space 

 of a line or less, below which the striae are lost in the dense enamel-like 

 coating wliich covers both faces of the crown; posterior face of crown 

 rhombic, outline of base similar to that of crest, and bordered by five 

 strongly marked imbricating folds, which are conspicuously arched down- 

 wards in the middle and more or less deflected at the lateral extremities; 

 anterior face broadly rhomboidal, basal fold consisting of four or five ob- 

 scurely marked imbrications, gently curved downwards in the middle and 

 again at the lateral extremities; the upper edges of the imbricating folds 

 are minutely crenulated; root broad, compressed at the edges, rapidly 

 tapering from the lateral shoulders, and terminating in a blunt rounded 

 point. Upon much worn surfaces the cro\fn is finely punctate. 



Indies. 

 Length, nearly 2 



Greatest breadth of crown, about 1.60 



Height of anterior face of crown. 95 



Height of posterior face, 1 . 28 



Breadth of root across the lateral shoulders, about. .. 1.1 



