304 



be a mistake ; or, if they hud, that they were, perhaps, accidental in their 

 occurrence in that formation, and had probably been derived from some con- 

 tiguous Eocene deposit. The frequent repetition of the same thing has led 

 me to view the specimens as having really pertained to Cretaceous fishes. 

 The absence of the lateral denticles would refer the teeth to the genus Oxy- 

 rhina, and the general form and other characters rather to the genus Lamna, 

 May the teeth not be regarded as having belonged to Oxyrhina ancestors of 

 some of the later Lamnse 1 



Fig. 44, Plate XVIII, represents a tooth which lies imbedded in a portion 

 of gray rock, obtained by Dr. John L. Leconte from the Cretaceous forma- 

 tion three miles east of Fort Hays, Kansas. The specimen is perfect and 

 unabraded. In all respects it is like the teeth of Lamna cuspidata of the 

 early Tertiary deposits, except that it is devoid of lateral denticles, and pre- 

 sents no trace of ever having possessed them. 



Fig. 45 represents a tooth, which lies in a block of chalk, from Sussex, 

 England. The specimen is preserved in the Museum of the Academy of 

 Natural Sciences of Philadelphia. Like the former, it closely resembles the 

 teeth of L. cuspidata, but exhibits no trace of lateral denticles. 



Figs. 46, 47 represent two teeth which the writer found with the skeleton 

 of Hadrosaurus Foulkii and shells of Exogyra costata, Ammonites placenta, 

 &c, in clay near Haddonfield, Camden County, New Jersey. These speci- 

 mens, unworn and perfect, except in positions having no relation with the 

 point in question, are identical in character with the teeth of Lamna -ele gam 

 of the early Tertiary deposits, except that they exhibit no trace whatever of 

 the existence of lateral denticles. 



Figs. 48, 49 represent two teeth selected from eight specimens obtained 

 by Dr. William Spillman from the Cretaceous formation near Columbus, Mis- 

 sissippi. Most of the specimens are complete and well preserved, and in no 

 instance exhibit traces of lateral denticles, while in all other respects they are 

 like the teeth of L. elegans. 



Seven specimens of teeth from the Cretaceous formation of Green County v 

 Alabama, presented to the Academy of* Natural Sciences of Philadelphia by 

 Dr. Joseph Jones, also agree with those of L. elegans, except that they have 

 no lateral denticles. 



In a collection of similar teeth, presented to the Academy by William M. 

 Gabb, in all the specimens' retaining the root, twenty in number, the lateral 



