65 



Thickness near inner border, at mid-lengtli -038 



Length of bone underlying the squamosal (imperfect) -502 



Breadth of same at mid-length , ■ 064 



Greatest thickness at mid-length .' • 030 



With the parts of the head, shown in fig. 18, was also found an anterior dorsal 

 vertebra (fig. 19), of rather small size. The faces of the centrum of this vertebra are 

 slightly concave. 



Next following is the description of a 

 right mandibular ramus, found separately 

 in 189*7, but agreeing in size with the one 

 depicted in fig. 18. 



Eamus of lower jaw (right). Cat. 

 No. 284. 



Eamus of lower jaw (plate XVIII, 

 figs. 1 and 2) stout, with an inward bend 

 at mid-length, low and thick behind, 

 elevated and laterally compressed in front 

 where the inner surface is shallowly con- 

 cave. Excavated posteriorly below for 

 nearly one-third of its length, the excava- 

 „,„,„.,, , , , ( ,, I . , . tion extending upward along the back 



Fig. 19. — Autenor dorsal vertebra or Monodoimis cauaaen.as, . •^'^^^'■ 



one-fourth the natural size. A, front view ; B, left side Stirface of the COroUoid prOCesS, aud an- 



view; a, anterior face of centrum; d, diipophysis ; h, teriorly as the mandibular canal leadiuo" 



facet for head of rib ; « neural canal; .9 neural spine ; forward to the mandibular groOVe in the 

 t, facet for tubercle of rib ; z, prezygapophysis ; z, post- i i mi t ^ 



zygapophysis. " lower border. Ihe dentary canal, between 



theouter alveolarwall and theouter surface, 

 enters from the upper and anterior part of the excavation by a large opening. Coronoid 

 process stout, upright, hooked forward and flattened laterally above, its outer, upper 

 suiface rugosely striated. A broad, low ridge, least defined toward the centre, runs at 

 about mid-heigth, along the outer side, the surface, in a general way, above and below, 

 retreating obliquely inward. The dental chamber, straight, starting at a low level behind, 

 inclined strongly uiiward and slightly outward toward the front, its lower edge making 

 an angle of about 20° with the lower border. Alveolar grooves in outer wall of dental 

 chamber, deeply impressed toward their upper ends by a second series of groove termina- 

 tions, an evidence of two roots in the teeth, belonging to this jaw, such as are characteristic 

 of some of the species of the CeratopsidcB ( Xgathaumidce). Height of dental chamber much 

 reduced forward. A number of large foramina present in the outer surface. Front border, 

 as viewed from the side, sinuous, rugose for its union with the predentary bone. Twenty- 

 three alveolar grooves are present in the dental chamber (imperfect posteriorly) of the 

 specimen figured. A small symphyseal surface is present in the front, lower border. 



Measurements of ramus of lower jaw. 



M. 

 Extreme length a^ mid-height • 39s 



Depth at mid-length -116 



Distance from upper border, a little in advance of front end of dental chamber, 



to lower posterior border of symphyseal surface - . . ._ -137 



Height of facet for articulation of predentary bone • 096 



Distance from top of coronoid process to lower border -193 



