138 CRETACEOUS AND TERTIARY FISH. 



which has same form in both, though two dentinal faces latter 

 possesses are those of true Bdaphodon. 



Formation and locality. _ Known only from the type, described 

 above, a right mandibular, from the marl near Mount Holly in 

 Burlington County, referred to by Cope as "Greensand No. 5" 

 [but now recognized as the combined Navesink-Hornerstown 

 marl bed, K.] now in the American Museum at New York. 



Leptomylus dens us Cope. 



Leptomylus densus Cope, Proc. Boston Soc. Nat. Hist., XII, 1869, p. 313. 

 Birmingham, N. J. Cretaceous marl pits. 

 Cope, Rep. U. S. Geol. Surv. Terr. II, 1875, P- 281. (Birmingham, N. J. 

 Greensand No. 5.) 



Mandibular with front end prolonged, slightly narrowed, hind 

 face plane, and transversely concave longitudinally. When ex- 

 ternal edge rises internal falls off, and narrow dentinal area di- 

 rected obliquely upwards and inwards. Inner face, above an 

 anterior thickened margin as deep as prolonged beak, concave, 

 but again convex near superior margin. Marked with obscure 

 curved, coarse lines parallel to hind outer edge. Lower or front 

 edge a contracted ridge, inner plane vertical and upper part of 

 inner face expanding upwards. Dentinal column supporting 

 tubercle large as a goose quill. No other columns. Length 

 from first point about 140 mm. (From Cope.) 



Cope also describes a palatal he thinks may belong to this 

 species. It differs from Edaphodon in the presence of two very 

 narrow dentinal bands, which are opposite and parallel, one on 

 the outer margin and the other within the inner margin of the 

 bone. Form much depressed and spade-like, superior face 

 scarcely descending regularly to edge. Outer margin expands an 

 inch behind end and beveled off from continued width of upper 

 face, latter showing slight longitudinal striae. Proximally usual 

 large groove. 



Formation and locality. Known only from Cope's account, 

 reproduced above, based on a mandibular from the "Greensand 

 No. 5" [the Navesink-Hornerstown marl bed, K.] of Birming- 

 ham in Burlington County (J. Gaskili). Also a supposed palatal, 

 with same data. 



