164 PROCEEDINGS OF THE ACADEMY OF [1888. 



tooth ; the remaining teeth successively decreasing. In the under 

 jaw the first tooth is small, about one-half the size of the next, which 

 is the largest ; and then the others successively decrease. 



Miiller and Henle, Abbott, and Giinther intimate that in Odon- 

 taspis, in the upper dental series, there are one or two small teeth 

 after the third large tooth. In none of our specimens are there two 

 small teeth in this position, but after the single small tooth there is 

 a hiatus, in different jaws ranging from a third to more than half an 

 inch, which presents no trace of a tooth. This hiatus is unusual in 

 the dental series of sharks ; and it perhaps gave rise to the inference 

 and consequent assertion that it is normally occupied by a second 

 small tooth. In the figure of the dentition of Odontaspis taurus as 

 given by Miiller and Henle, notwithstanding their statement, a single 

 small tooth appears after the upper third large tooth, in accordance 

 with what we observe in 0. Uttoralis. In 0. taurus, the first tooth 

 in both jaws is represented as being nearly equal and about a third 

 less than the adjoining teeth ; and the upper third and lower second 

 teeth appear as the largest of the series. 



