FROM THE PHOSPHATE BEDS OF SOUTH CAROLINA. 239 



The lateral hexagonal teeth are longer than broad, and each is impressed along the 

 middle. 



The upper surface of the dental pavement is concave fore and aft, and is con- 

 vex or slopes off laterally from the median line. The thickness of the pavement 

 on the median ridge is 9* lines; on the lateral ridges 5i lines. 



Another specimen, represented in figure 11, PI. xxxi., also from Monmouth Co., 

 N. J., presented to the Academy by the late Dr. J. H. Slack, perhaps belongs to 

 the same species as the preceding, though it exhibits some important differences. 

 It is likewise an upper dental plate, and is worn away at the anterior part from the 

 attrition of food. It retains seven median teeth, together with three small teeth 

 of the first row of one side, and in its present condition measures two and a half 

 inches long. 



The pavement is considerably narrower in proportion with its length than in 

 the former specimen, while the thickness in each is nearly the same. Seven median 

 teeth in the first described plate measure together 31 1 lines by 35 lines in breadth; 

 in the specimen under examination the same number of teeth measure 29| lines 

 by 26 lines in breadth. The median convex ridge of the triturating surface is 

 equally prominent, but the lateral elevations are nearly obsolete. The transverse 

 sutures present but one flexure corresponding with the median one backward in 

 the former specimen. 



The median teeth range from 4| to 4| lines fore and aft. The thickness of the 

 pavement on the median ridge is 8f lines; and at the sides 5| lines. 



Prof. Marsh has noticed a specimen of a dental plate, in the Proceedings of the 

 American Association for the Advancement of Science, 1869, from the eocene green 

 sand of Monmouth Co., under the name of Myliobates bisulcus, to which one or 

 other or perhaps both of the former may also belong. He remarks that it has 

 " the central row of teeth marked along the median line by a deep groove. In 

 other respects the dental surface is remarkably smooth and flat." These characters 

 render it probable that it may be the inferior dental plate of the same species as 

 that to which the former specimens pertain. 



Myliobates serratus. 

 Leidj: Proceedings Academy Natural Sciences, 1855, 395. 



This species was named on the specimen of a dental plate^ represented in figure 

 5, PI. xxxii., which was found in the marl of Pemberton, Burlington Co., N. J., 

 and was presented to the Academy by Dr. Charles H. Budd. It resembles most 

 the dental armature of Myliobates toliapicus^ Ag., and M. suturalis, Ag. 



