64 PALEONTOLOGY OP OHIO. 



Heliodus Lesleyi (n. sp.). 



Plate LVIII., Fig. 18. 



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

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

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

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

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

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

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

 wliich borders the central furrow liave 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 ]ower 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 backward about four lines, and 

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

 tlie tooth was doubtless covered with integument. 



The more important features of this tooth and its relations 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 

 Geological Survey of that State. 



