t antero-posterior 

 Diameter of crown \ . „ „ „„ 

 ( transverse 



of the successional teeth; the former is often slightly concave, 

 and is the seat of most rapid attrition. The lateral facets disap- 

 pear at a distance below the apex, where the non-cutting side is 

 strongly convex, and covered with a coarsely rugose cementum ; 

 the rugosity including pits. 



Measurements. M. 



Length, of a shed tooth Oil 



.010 

 .012 



Width of facet for successional crown 006 



"Width of posterior facet 005 



Width of cutting face of another near apex . . . .008 

 Antero-posterior diameter of do. at do 010 



The prominence of the median angle with other points distin- 

 guishes this species from the Cionodon arctatus. The size is larger 

 than that of the known specimens of that species, equaling that of 

 the largest of the order. (See Report of U. S. Geological Surv. 

 Terrs. II., 4to, for description of genus Cionodon.) 



Specimens of this species have been referred by Dr. Leidy to his 

 Trachodon mirabilis. 



Diclonius calamarius, sp. nov. 



This species, as represented by teeth, is the smallest of the 

 genus, but the adult size is a point, however, not easily deter- 

 mined among extinct reptiles. The teeth are slender, and the 

 front has parallel borders and a median keel. The borders are 

 entire, and, in two of the crowns, twisted slightly round the long 

 axis of the tooth. The keel is thus twisted also, and towards the 

 base, when it becomes quite low, is nearer one border than the 

 other. The back of the tooth displays two lateral facets, sepa- 

 rated by a narrow median facet. The former have a thin, deli- 

 cately rugose, cement investment, with a minute rugosity; the 

 latter is smooth in the specimens, apparently from friction. The 

 characters of this saurian readily distinguish it from its congeners. 



Measurements. m. 



Length of portion of crown 012 



( antero-posterior 004 



.004 



Diameter of crown -J , 



Monoclonius crassus, Gen. et sp. nov. 



Char. Gen. — Teeth with obliquely truncate face and distinct 

 root, which is grooved for the successional tooth on the front. 



