289 



lower border very oblique to the interior, which is longitudinally grooved. 

 The portion preserved includes five dentinal columns, the inner borders more 

 or less exposed. The median or interior column is the largest. This piece 

 is similar in generic characters to that of I. mirificus. 



This species is quite near to the I. inonolophus, differing in the uniform 

 convexity of the outer face, which is in the latter partially concave. A max- 

 illary bone from the locality from which the latter was derived differs from 

 that of the I. eoccenus in the small size of its areas ; its reference is not cer- 

 tain. 



From the Eocene greensand of New Jersey. 



ISCHYODUS MONOLOPHUS, Cope. 



Proceedings of the Boston Society of Natural History, 1869, p. 314. 



Greensand, No. 5, of New Jersey, near Barnesborough ; 1. C Voorhees, 

 discoverer. 



ISCHYODUS INCRASSATUS, Cope. 



This large species has a general resemblance to the I. mirificus, differing 



in important details. Thus, the apex of the inner dentinal area marks only 



the middle of the anterior outer instead of the anterior extremity. The latter 



is horizontal, standing on a considerable tuberosity, which is removed within 



the outer border of the jaw, so that the latter is not angulated there as in 



some similar species, as /. fecundus. The convexity of the lower half of the 



outer face of the jaw is very strong, so that the lower border is thicker than 



in any other species here enumerated. The inner area is undivided, and 



slopes to the inner edge of the jaw; it is of medium extent. The symphy- 



seal face is a narrow border along the inner edge of the beak ; the inner face 



of the jaw is plane, and is longitudinally striate with low ridges. The beak 



is but little curved outward. 



Measurements. 



M. 



Length of the fragment 0. 125 



Length to the anterior outer area 0. 060 



Depth at the anterior outer area 0. 045 



Width at the anterior outer area 0. 030 



Width at the middle of the beak 0.021 



Depth at the middle of the beak 0.022 



Width of the inner area obliquely 0. 028 



But one specimen of this species has come under my observation, and it 

 was found at Hornerstown, New Jersey, by John G. Miers, in the green- 

 sand of Cretaceous No. 5. 

 37 c 



