286 



narrow, and extends a little anterior to the anterior border of the anterior 

 outer The apex of the jaw is obtuse, and the terminal area is on its 

 superior aspect, is oval, and continues as the edge of a lamina along the outer 

 margin of the beak. There is no symphyseal plane, and the whole jaw is 

 much compressed and narrowed. It has much the form of that of Lepto- 

 mylus forfex, and approaches the I. laterigerus. 



Measurements. 



Length of the fragment (total) 0.070 



Depth behind 0.080 



Depth at the posterior outer area 0. 064 



Depth at the anterior outer area 0. 041 



Depth at the inner area 0. 024 



Depth of the inner face behind 0. 027 



Width at the inner area 0. 018 



Width behind at the inner angle . 0.021 



Width behind near the summit 0.015 



Hornerstown, New Jersey. Greenland of No. 5. 



ISCHVODUS TRIPARTITA, Cope. 



/. mirifivus, " Leidy," Cope, Proceedings of the Boston Society of Natural History, 1809, p. 

 314, not of Leidy. 



This species was embraced in the specimens mentioned by Professor 

 Leidy as having furnished the type of his I. mirificus; and, as his first descrip- 

 tion does not specify to which of them he referred, I had supposed that those 

 belonging to the present species were the cues described. As Dr. Leidy has 

 subsequently selected a different one as his type (in Report of Hayden's 

 United States Geological Survey), it remains to give the present Chiraseroid 

 a new appellation. 



The 7. tripartilus is the largest of the American species of the genus, 

 and is not uncommon in the greensand of No. 5. The tripartite division of 

 the inner area is a prominent feature: the three columns are united at their 

 adjacent borders: and the outer is more than twice as large as either of the 

 two interior ones. The latter are separated from the inner angle of the jaw 

 by an oblique plane of some width, a character which is only seen in the /. 

 longirostris among the other species of this genus known to me. The exter- 

 nal areas are narrow: the posterior quite small. The anterior is elongate, and 

 extends far in advance of the inner areas along the summit of a horizontal 

 ridge, which is produced as a strong step of the outer margin. The outer 



