64 PALEONTOLOGY OF OHIO. 



Heliodus Lesleyi (ll. sp.). 



Plate LYIIL, Fig. 18. 



Upper dental plate rounded or hippocrepiform, 1| inches in lengtli 

 and breadth ; triturating- surface more than a half circle, highest in the 

 centre, where it forms a broad sraootli boss; from this radiate eight 

 tuborculated ridges, four on either side of the median line, which is 

 marked by a deep and smooth furrow. The ridges on each side differ 

 fiuiong themselves, but are symmetrical with those on the other side, the 

 lateral ridges being shortest, and bearing several tubercles, while the pair 

 which borders the central furrow have but a single tubercle at the 

 extremity of each. On both sides of the central boss the crown of the 

 tooth is worn in a shallow, rounded depression by the opposing teeth of 

 the lower jaw. The posterior margin of the crown is nearly straight, 

 and is slightly crenulated at the centre. This is bordered by a sloping 

 surface which extends downward and l)ackward about four lines, and 

 expands laterally to form low, winglike projections. This portion of 

 tlie tooth was doubtless covered with integument. 



The more iinportant features of this tooth and its .relatioUj^ to allied 

 forms, are given in the generic description. It was obtained by Mr. 

 Andrew Sherwood, in the Upper Chemung rocks of Northern Pennsyl- 

 vania, and is named in honor of Prof. J. P. Lesley, the Director of the 

 (xeological Survey of that State. 



