MONOCLONIUS DAWSONI. 



91 



Measurements of scapula and coracoid. 



Scapula with coracoid (left). Cat. No. 506: Mm - 



Extreme length of scapula with coracoid in line with back edge of shaft 0. 879 



Length of scapula 711 



Length across glenoid cavity 150 



Length of glenoid cavity along curve. 204 



Breadth of glenoid cavity at suture between scapula and coracoid - — . 078 



Breadth of glenoid cavity near either end 096 



Breadth of scapula at junction with coracoid, inner surface. , . 175 



Breadth of scapula at junction with coracoid, outer surface 149 



Breadth of scapula at upper end of glenoid cavity — . 238 



Breadth of scapula at mid-length . 113 



Breadth of scapula at upper end 184 



Breadth of coracoid at lower end of glenoid cavity. .. 223 



Thickness of scapula at upper end near front border 025 



Thickness on base of ridge above upper end of glenoid cavity 060 



Thickness at lower end of glenoid cavity. 060 



Thickness of coracoid in concavity below foramen 020. 



Width of foramen, inner end. 014 



Height of same, inner end 030 



Width of same, outer end 025 



Height of same, outer end 040 



The rostral bone figured on PI. XX and the small predentary bone 

 (PI. XIX, figs. 5 and 6) [PI. XX, figs. 2 and 3] were found separately, 

 and may with some probability of correctness be referred to this species. 

 A large ilium is figured toward the end of this report. 



This species is named in honor of Dr. George M. Dawson, C. M. G., 

 late director of the Geological Survey of Canada. 



From the above description it will readily appear 

 that the fragmentary skull (No. 1173, Geol. Surv. 

 Canada) must be considered as the actual type of the 

 present species, on which alone we must depend for 

 the determination of its distinctive characters. The 

 posterior crest and associated horn core, as well as 

 the scapula and coracoid, ilium, rostral, and predentary 

 bones provisionally associated with the type may 

 have pertained to the same species, but of this we 

 can not be certain, and since they were all found 

 disassociated they may possibly have pertained to 

 one or more different species. However this may 

 prove to be, any characters which this collateral 

 material may show can not be taken as certainly 

 diagnostic of the species until such time as the dis- 

 covery of additional and more complete material shall 

 conclusively demonstrate that these particular types 

 of parietal crest, scapula, etc., were associated with 

 that pattern of skull shown in the actual type. 



The type (No. 1173, Geol. Surv. Canada) consists 

 of a very fragmentary skull with large and somewhat 

 compressed nasal horn core curved backward, ovate in 

 cross section, with the broad end of the oval directed 

 anteriorly. The orbit is nearly circular, and there 

 still remains in the type the base of a small rudimen- 

 tary supraorbital horn core. This rudimentary horn 



core is flattened on its external surface as in the cotype of Monoclonius crassus Cope. About 

 1 inch of the apex of this horn is wanting in the present specimen. A fragment of the parietal 

 is preserved showing three or four of the marginal undulations. These resemble those seen 

 in the type of Monoclonius crassus Cope, and I am inclined to regard the present species as 



Fig. 94. — Trachodon sacrum provisionally associated with 

 Monoclonius dawsoni by Lambe; superior view, less 

 than one-seventh natural size, nc, Neural canal; d, 

 diapophysis; np, neural platform; ns, neural spine; 

 i, interspace. After Lambe. 



