134 



CRETACEOUS AND TERTIARY FISH. 



mandibular edge, and in front begins slightly behind outer den- 

 tinal area. Latter similar, and apparently large. Length about 

 80 mm. 



This fragment is in the collection of the Geological Survey 

 and is without data. It suggests B. incrassatus and may be iden- 

 tical or referable to some similar species as yet undescribed. 



Formation and locality. Not given. 



Genus BRYACTINUS Cope. 



Bryactinus Cope, Rep. U. S. Geol. Surv. Terr., II, 1875, p. 282. Type Bry- 

 actinus amorphus Cope, monotypic. 



This genus differs from Bdaphodon in having several dentinal 

 areas exposed along outer edges, the apical tube exposed at both 

 extremities and the excavation of posterior half of inner face. 



A single extinct species known. 



Bryactinus amorphus Cope. 



Bryactinus amorphus Cope, Rep. U. S. Geol. Surv. Terr., II, 1875, p. 282, 

 PI. 45, fig. 12. Hornerstown, N. J. Greensand of No. 5. 

 Hussakof, Bull. Amer. Mus. Nat. Hist., XXV, 1908, p. 37, fig. b (type). 



Fig. 83. — Bryactinus amorphus Cope. (Type, from Hussakof.) 



Dental plate triangular, base representing grinding face, not 

 level, but like others slightly convex. Opposite angular ridge 

 only extends half jaw length, then sinks and exposes hind end 

 of apical column of dentine. On grinding surface along outer 

 border three other columns issue, not parallel in their courses, but 



