56 



M. 



Width of the ilium at the front of the acetabulum , 0. 210 



Width of the ilium at the posterior expansion 0. 250 



Thickness above the acetabulum 0. 080 



AVidth of the acetabulum 0. 105 



Width of the basis of the ischium 0. 085 



Width of the shaft of a rib 0.062 



Other bones, not jet determined, will be included in the description in 

 the final report. 



This species was no doubt equal in dimensions to the largest known ter- 

 restrial saurians or mammals. 



HADROSAURUS, Leidy. 



Hadeosaueus mikabilis, Leidy. 



Numerous bones of Dinosauria, from the Milk River, British America, 

 submitted to me by Dr. G-. M. Dawson, of the British North American 

 Boundary Commission, embrace specimens appropriate to this species, but 

 not certainly referable to it. The locality is nearer to the bad lauds of Judith 

 River, from which the H. mirabilis was procured, than to any other exposure 

 of the Fort Union beds. 



There are portions of femora, humeri, and ilia, but the only piece suffi- 

 ciently characteristic for description is a median caudal vertebra. The 

 inferior ridges and facets for chevrons are strongly developed ; the latter 

 appealing at both ends. The anterior articular face is plane ; the posterior, 

 concave. The centrum is deeper than wide, slightly narrowed below ; no 

 traces of diapophyses. Length, m .060; depth of articular lace, ,u .O77 ; 

 width of articular face, m .071 ; length of base of neural arch, m 038. The 

 reference of this vertebra is uncertain, but it seems too small for the H. occi- 

 dentalis, although in the opisthocoelian character it is similar. 



Hadrosaueus occidentalis, Leidy. 



Referred by Professor Leidy to a distinct genus under the name of 

 Thespesius, on account of the slightly opisthoccelian character of the large 

 caudal vertebrae. Teeth unknown. 



Fragments of a large Dinosaur, from Colorado, were found associated 

 with species of tortoises identical with those found in Dakota, in the horizon 

 which contains the H. occidentalis (see under head of Cionodon arctatus), and 

 may possibly belong to it. I have no identical parts in the two for com- 

 parison. 



