FROM THE PHOSPHATE BEDS OF SOUTH CAROLINA. 235 



In addition, the triturating surface of the plate of M. Bolmesii, if one can form 

 a correct idea of it from the figure, appears even, as is usually the case, instead 

 of being transversely ridged, from the successive inclination of the median plates, 

 as in the specimen described. 



The second of the two specimens, above referred to, is likewise a dental pave- 

 ment from the floor of the mouth, and is represented in figure 2, PI. xxxiii. 

 It is composed of ten median teeth, and some of those of the first lateral row of 

 small ones on both sides. The dental plate has about the same form as the pre- 

 ceding, but is of less breadth and much thinner, and, therefore, at least may be 

 inferred to have belonged to a smaller individual. The triturating surface is 

 feebly depressed along the middle, but has the same uneven character, though in 

 a less degree, due to the slight elevation of the anterior borders of the median 

 teeth, and the successive slight inclination of their surfaces. The transverse 

 sutures are less straight than in the former specimen, especially the more posterior 

 ones, which appear slightly bent forward, and also appear more open or wider. 



On the triturating surface seven median teeth occupy an extent equal to the 

 same number in the preceding specimen. The first and last of the series measure 

 ^ lines. The breadth of the median teeth is about SO lines. The thickness of 

 the dental plate in the middle is 7| lines. 



The inferior surface of the base of attachment slopes off from the median line 

 with a slight inflection. 



Another specimen, represented in figure 3, PI. xxxiii., which may probably 

 belong to the same species as the foregoing, is a superior dental plate, and was 

 recently presented to the Academy by Mr. George S. Lewis. Its upper or attach- 

 ing surface has adherent a quantity of calcareous rock, like that of the eocene 

 marl rock, which underlies the Ashley phosphate beds. This serves to confirm 

 the information derived from Prof. F. S. Holmes, that the specimen and others 

 similar are eocene fossils. 



The dental pavement consists of about a dozen median teeth together with 

 part of the contiguous two rows of lateral teeth at the sides. The triturating 

 surface is well arched fore and aft, and is also in a less degree convex transversely. 

 The median teeth and intervening sutures are nearly straight transversely, but 

 curve backward at the extreme ends. The conjoined edges of the median teeth 

 are slightly prominent, giving the transversely ridged appearance more obvious in 

 the preceding specimens of the fioor of the mouth. Feeble ridges extend the 

 length of the triturating surface. 



The lateral teeth extend the convexity of the sides of the triturating surface. 



