396 [August, 



rugosus is prominently convex and longitudinally wrinkled, especially at the ex- 

 tremities of the median dental plates. The latter are united by convex suture 

 directed forward. The attaching surface of the specimen is flat. 



Diameter of the median plates transversely 2 inches and 4 lines, antero-pos- 

 teriorly 4^ to b} lines. 



Locali'g. Discovered by Mr. Horner in the Marl of New Egypt, New Jersey. 

 T. A. Conrad. 



3. Myliobates obesus. Based upon a pair of median dental plates of a species 

 smaller than M. rugosus, and comparatively more convex in its sutures and its 

 triturating surface. 



The estimated transverse diameter of the median plates was about 16 lines, 

 the antero-posterior diameter is 3^ lines. 



Locality. Discovered by Dr. Charles H. Budd, in the Green sand of Burlington 

 Co., New Jersey. 



4. Zygobates ddbids. Based upon numerous specimens of isolated dental 

 plates. The median dental plates are comparatively wide compared with their 

 transverse breadth, their triturating surface is convex, and the attaching surface 

 concave and parallel with the former. The lateral dental plates of the first row 

 present a corresponding width and breadth to the median plates. Their tritu- 

 rating surface is convex and slopes off laterally, and their attaching surface is 

 straight. 



Transverse diameter of median plates 6 to 16 lines, antero-posterior 2 to 4J 

 lines, thickness 1|- to 3 lines. Transverse diameter of lateral plates of the first 

 row up to 13 lines, antero-posterior up to 4 lines. 



Locality. Discovered by Capt. Bowman, U. S. A., in the sands of Ashley 

 river, South Carolina. Probably washed from eocene beds. 



5. Aetobatis perspicuds. Based upon a specimen consisting of one half of 

 an isolated dental plate of the upper jaw. Although the fragment is a very small 

 one, it is very characteristic. The triturating surface is smooth, excepting, how- 

 ever, the accidental scratches ; and it is perfectly level antero-posteriorly, and 

 is slightly convex transversely ; and the attaching surface is parallel with the 

 former. The anterior and posterior margins form the segment of a circle bent 

 at a very obtuse angle. The outer extremity of the dental plate is abruptly 

 truncated, and the enamel turns down laterally to the extent of a line. The 

 antero-external angle forms a projecting heel, and the corresponding posterior 

 angle presents a concave fossa for the reception of the contiguous heel of the 

 posterior dental plate. 



Estimated breadth of the upper dental series 21 inches, antero-posterior width 

 cf the dental plate at its middle 4 lines, thickness 4 lines. 



Locality. Discovered by Dr. J. L. Burtt in the Green Sand of New Jersey. 



6. Aetobatis bximius. Based upon a specimen consisting of one half of four 

 median dental plates, with a corresponding row of lateral plates. The median 

 plates are perfectly level on the triturating surface, except at their outer ex- 

 tremity, where they are abruptly rounded off. The sutures are slightly bow 

 formed, and of the two sides of the outer extremities that anterior is the longest. 

 The species has but a single row of lateral plates, which are convex at their 

 outer border, and are angular within to join two contiguous median plates. 



Estimated transverse diameter of the dental series, including the small lateral 

 plates 23 lines, antero-posterior diameter of the median plates Z\ lines. 



Locality. Discovered by Capt. Bowman, U. S. A., in the sands of Ashley 

 river, S. C. Probably washed from Eocene beds. 



7. Odax carolinensis. Based upon numerous specimens, consisting of por- 

 tions of the jaws and pharyngeal bones, with teeth. External extremities of the 

 maxillary denticles very distinct from one another, convex, six in number in a 

 vertical row of 5- lines. Pharyngeal bones triangular, with two short equal 

 sides, and the long side measuring from 6 to 8 lines, densely furnished with teeth 

 resembling in form the corresponding ones of Pogomas. 



