292 



ISCHYODUS MIEKSII. 



? Dipristis miersii, Marsh, Proceedings of the American Association for the Advancement of 

 Science, 1870, p. 230. 



The mandible of this species is peculiar in several respects. The beak is 

 long and straight, and the outer face is concave to the base of the anterior 

 outer dentinal area. The anterior outer dentinal area is not elevated above 

 the grinding-face in front of it, and is near the edge of the jaw. The inner 

 area is acuminate, and produced beyond it, and extends to the inner border. 

 The inner face is slightly concave, with a broad symphyseal bevel along the 

 inner margin. The apical area is the end of a curved laminar column The 

 long axis of the jaw is straight, as is the inferior border, differing from allied 

 species, which are more or less curved. Lower border transversely thickened. 



Measurements. 



If. 



Length of the fragment 0. 100 



Length to the anterior outer area 0. 055 



Depth at the anterior outer area 0. 030 



Width at the anterior outer area 0. 022 



Width of the middle of the beak 0.015 



Depth at the middle of the beak 0.015 



Diameter of the lower border at, the middle of the beak 0. 017 



A broken maxillary and a dorsal spine accompany this mandible. The 

 latter is identical with the ichthyodorulite described by Marsh, as above, as 

 Dipristis miersii. My specimens are from the locality from which the latter 

 was derived, viz, the excavations on the property of John Gr. Miers, at Hor- 

 nerstown, Monmouth County, New Jersey. 



IsCHYODLS DIVARICATUS, Cope. 



Proceedings of tin- Boston Society of Natural History, 1669, \>. 315. 



Besides the typical specimen, three others have come into my hands. 

 They exhibit the general peculiarities, as the uninterrupted masticatory sur- 

 face, the small external areas, the anterior subround, and opposite or behind 

 the apex of the very large inner; the narrowed beak making an angle with 

 the posterior part of the jaw. and penetrated by a laminar column of little 

 width. Size rather less than that of /. fecundus. 



New Jersey greensand, Xo. 5, from near Hornerstown. 



