1869.] 317 [Cope. 



cartilaginous table below, but is connected with that usual position 

 by a broad obliquely horizontal bony lamina. This lamina is not 

 continuous with the masticatory surflice above, but is depressed be- 

 neath its plane so that the lamina and masticatory band of the tooth 

 next posterior may rest upon it. The grinding plate is thus formed 

 of a number of transverse bands as in Aetobatis, which are sup- 

 porteti on oblique plates, arranged tile or shingle-like, and whose 

 origin is far posterior to their exposure. There appears to have been 

 no supplementary series of teeth. This inferior and non-exposed por- 

 tion of the laminiform tooth is longitudinally grooved, those of the in- 

 ferior surface being adapted to those of the superior surface of the 

 next preceding. The anterior margin of the masticatory band is also 

 suture-like, for a similar reason. 



This remarkable genus appears to be for the first time brought to 

 the notice of naturalists. Its affinities are obviously to Aetobatis. 



Char, specif. I suppose the single tooth preserved, to belong to 

 the palatal series ; it is entirely transvei'se, and without alteration 

 at the extremity except that it thins off. The masticatory surface is 

 slightly convex, and little more than half as wide as the laminar plate 

 which supports it . This plate rises from the horizontal at an angle 

 of about 35°. The laminsB of insertion are ovate pai-allelogrammic, 

 and attached by a narrower base; they are remarkably coarse, there 

 being five included in a length of two lines. A projecting angle 

 continues the upper surface of the superior plate above these laminas 

 while a groove on the inner junction of the two receives the same of 

 the next tooth. Immediately above this a delicate ridge bounds it. 

 The general surface is nearly plane. 



As one exti'emity is broken off the proportions cannot be readily 

 ascertained, but if they bear any relation to the coarseness of the in- 

 ferior laminae, the transverse extent of the plate has been consider- 

 able. 



Lines. 



Length of plate ? 18 



Width of plate 4 



Width of masticatory face 1.8 



Thickness of masticatory face 1 



Thickness at basal laminas 2 



This ray was found by Reuben Davis, at his marl pit in the Mio- 

 cene formation near Shiloh, Cumberland Co., New Jersey, name 

 from nUlvdog, a tile or shingle. 



