354 



enameloid surface is strongly wrinkled longitudinally, and the lateral denticles 

 are directed downward. 



From the Miocene formation of Virginia. Specimen discovered by Mr. 0. 

 M. Smith in the blue clay beneath the city of Richmond. 



MYLIOBATES. 



Myliobates . 



Indicated by the basal portion of a caudal spine, represented in Figs. 52, 

 53, Plate XXXII. In its relation of breadth to length, in comparison with 

 the spines of ordinary rays, it would appear in the complete condition to 

 have been upward of 8 inches in length. The specimen, however, becomes 

 rather more abruptly narrowed at its upper broken extremity than appears in 

 ordinary spines, so that it may have been proportionately shorter than usual. 



The transverse section has almost the Greek e form. In front the spine * 

 is concave along the middle and convex at the sides ; behind it has the 

 reverse arrangement. The lateral denticles are directed downward and 

 backward. The anterior enameloid surface is strongly wrinkled along the 

 middle groove, but not so much at the sides, except at the base of the spine. 

 The posterior surface is moderately ridged. 



Specimen found with the preceding in the blue clay of the Miocene forma- 

 tion of Virginia. From Mr. C. M. Smith. 



