102 CRETACEOUS AND TERTIARY FISH. 



The existing species, about 10, distributed in tropical seas. 

 About five extinct species have been described. 



RhinoptEka dubia Leidy. 



Dental plate depressed, evidently upper or enameled surface 

 well convex and lower or basal surface equally concave, though 

 both surfaces evenly so. Enamel surface smooth, of usually even 

 thickness, and edges usually abrupt. Extremities of tooth form 

 rather obtuse angle, and apex would form medianly in vertical 

 diameter. Vertical diameter of enamel surface nearly one-seventh 

 of horizontal. Root not visible as enameled surface is viewed 

 from above, low, greatly depressed, sometimes moderately deep, 

 and uniformly concave. Vertical grooves rather variable, numer- 

 ous or moderate. Greatest breadth 46 mm. 



This species does not ever appear to have been noted from 

 New Jersey before. Many of my examples agree entirely with 

 Leidy's, but other specimens must be admitted somewhat pro- 

 visionally, as they are possibly teeth belonging to Myliobatis. 

 Known only from detached teeth or dental plates. ■ 



Formation and locality. The following examples in the collec- 

 tion of the Academy have been examined: Monmouth County 10 

 (W. Cleburne) and 2 (P. D. Knieskern) ; Vincentown, in the 

 marl of Burlington County 1 (C. B. Barrett), and 1 said to be 

 from the Miocene labeled "Bridgeton Pike" (C. C. Abbott). 



I have also examined some fragmentary dental remains in the 

 collection of the Geological Survey taken from well-borings at 

 214 feet on July 23d, 1909, on the beach front at Bradford Cot- 

 tage, Fortesque, in Cumberland County. From 200 to 214 feet 

 the shell-beds were in a tough, leathery mud, and in this horizon 

 were found the fragments of the present species. For informa- 

 tion and these specimens the Survey is indebted to Mr. S. P. 

 Foster, of Elmer, and Mr. C. Holaday, of Hornersville. A com- 

 parison with a large series of examples from the Maryland Mio- 

 cene, with which they agree in most respects, would point to 

 their beino- from the same formation. 



