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ART. XXV. — New species of Myliobates from the Eocene of South Carolina, with 

 other genera not heretofore observed in the United States. By Robert W. Gibbes, 

 M. D., Correspondent of the Academy of Natural Sciences of Philadelphia, &c. 



The family of Placoid fishes is found in abundance in the Tertiary formations. 

 In those deposits of South Carolina their teeth are particularly numerous, though 

 usually much broken. Among the Squalidce I have identified and described (with 

 those here noticed) ten genera and forty-five species ; — of Pristis I have published a 

 new species, and of Myliobates I have numerous fragments. Two species are 

 distinctly represented by specimens now noticed and figured. 



Of the genus Myliobates, Muller and Henle recognise five recent, while Professor 

 Agassiz has described fifteen fossil species, chiefly from the London clay. 



This genus is characterized by broad transverse teeth on a flat plate, bounded 

 laterally by three rows of narrow hexagonal teeth of equal length, united by fine 

 sutures. The arrangement resembles that of a tessellated pavement. 



The specimen figured PI. 42, figs. 1, 2, 3, has some resemblance to M. micropleurus, 

 Agassiz, but the lateral edges of the large transverse dental plates are more unequal, 

 as well as the form of the small ones, and the sutures are more curved backwards. 

 There is also perceptible a slight longitudinal flattening traversing the median line, 

 and it is more arched laterally. The lateral plates are too much broken for 

 description. The plates on the inner surface, PI. 42, fig. 2, are very regular, and on 

 the suture surface, PI. 42, fig. 3, are grooved in the form of a compressed V. 



It was found in the Eocene marl of Ashley river. South Carolina, and was 

 presented to me several years since by Mr. F. S. Holmes of Charleston, whose name 

 I attach to it, Myliobates Holmesii. 



The second species, PI. 42, fig. 4, was found in the Buhrstone (Eocene) formation 

 in the neighborhood of Orangeburg, South Carolina. It is more regular in the form 

 of the dental plates, which are less curved; the surface is more convex and flattened 

 by abrasion on the anterior third. It corresponds with no described species. It is 

 very common, as I have many fragments from various localities. The plates being 

 nearly straight it may be designated Myliobates transver salts. 



Ptychodus polygyrus, Agassiz. Five years ago I received from a friend a 



specimen oi Ptychodus polygyrus, (Pl. 42, figs. 5, 6,) supposed to be from Alabama. 



Lately Pr. Ames of Montgomery, Alabama, kindly forwarded to me another from 



the Cretaceous of Alabama, (PI. 42, fig. 5a,) which fixes the origin of the former 



individual. 



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