HOLOCEPHALI. 113 



jaw bv an oblique plane of same width. External areas narrow, 

 posterior quite small, anterior elongate and extends far in advance 

 of inner areas along summit of horizontal ridge, latter produced 

 as strong step on outer margin. Outer narrow border rises ab- 

 ruptly opposite middle of anterior area, causing masticatory 

 face to be very oblique at that point. Superior groove wide, outer 

 face not produced. Length 175 mm. (From Cope.) 



This is the largest American species of the genus and said to 

 be not uncommon. Hussakof has united Ischyodus longirostris 

 Cope with this species after an examination of the types. Ac- 

 cording to Cope the former differed, in having the inner den- 

 tinal area of the mandibular undivided, contracted and separated 

 by a plane from inner margin. Outer posterior area lost in his 

 specimen, but outer anterior opens in front of interior on hori- 

 zontal step which forms strong angle of outer border. This 

 border, therefore, abruptly excavated from that point forward, 

 while inner border descends gradually from inner angle. Ter- 

 minal area quite large and oblique. Symphyseal face large, in- 

 ferior border of jaw obtuse and jaw end narrowly compressed. 

 Palatal characterized by its small size and posterior position of 

 anterior dentinal area, so that bone appears more produced. Pos- 

 terior areas large. 



Formation and locality. The type, consisting of both mandi- 

 bulars and left palatal, are from Hurffville in Gloucester County. 

 The type of /. longirostris consists of one mandibular and one 

 palatal, both from Birmingham in Burlington County (J. C. Gas- 

 kill ). All are recorded as from the greensand No. 5. [According 

 to the present classification all would be referred to the Horners- 

 town marl, although at both these localities the Hornerstown and 

 Navesink marl beds are united in a single layer, so that they may 

 be from the Navesink or lower member, K.]. They are now in 

 the American Museum of New York. I have not examined these 

 specimens. 



Edaphodon laterigerus (Cope). 



Ischyodus laterigerus Cope, Proc. Amer. Philos. Soc. Phila., XI, 1869, p. 243. 

 Hornerstoivn, Nezv Jersey. Cretaceous Greensand No. 5. 

 Cope, Rep. U. S. Geol. Surv. Terr., II, 1875, pp. 284 288 (type). 

 Edaphodon laterigerus Hussakof, Bull. Amer. Mus. N. H., XXV., 1908, p. 38, 

 PI. 1, figs. 7-8 (type). 

 8 GEOL 



