30G 



ing is further known in relation to its locality, but I suspect it to he of Cre- 

 taceous age. Of known species, it bears most resemblance to the teeth of 

 Otodus semiplicatus, Ag., of the chalk of Europe. It also has some likeness 

 with a tooth from the chalk of France, represented in Fig. 11, Plate LXXVI, 

 of Gervais's Paleontologie Francaise. 



The crown forms a narrow demicone, with an expanded base supporting a 

 pair of inwardly-diverging denticles. The surface of the principal cone near 

 the base is plicated. The root is thick and deeply notched, and extends pos- 

 teriorly more than half the length of the tooth. The anterior surface of the 

 crown in the median line is as long as the base is wide, and is about one-fifth 

 greater than the posterior surface. 



The measurements of the specimen are as follows : 



Lines. 



Length of tooth at middle 16 



Length from ends of the root 21 



Breadth at ends of the root •. . \~>\ 



Length of crown in front 13 



Length of crown behind 10 



Breadth of crown at base 12f 



Holocephali. 

 EDAPHODON. 



In the extinct chimseroid fish Edaphodon the inferior maxillaries are pro- 

 duced anteriorly in a long beak, and the superior maxillaries are provided 

 with three large dental areas. In the allied genus Ischyodus the inferior 

 maxillaries are not prolonged in a beak, and the upper ones are provided with 

 four large dental areas. 



Edaphodon' mikificus. 



A species under the above name was indicated by the author in the Pro- 

 ceedings of the Academy for 1856, page 221. It was founded on eight speci- 

 mens of maxillaries obtained from the Cretaceous green sand of Burlington 

 County, New Jersey, by Professor George H. Cook, during the State geo- 

 logical survey. 



The inferior maxillaries, represented in Figs. 6 to 9, Plate XXXVII, are 

 about twice the length of the depth. The two rami converge in a curve, and 

 end together in a long, bird-like beak, (Fig. 6.) 



The outer surface (Fig. 7) of each ramus is lozenge-like in outline, defined 



