56 



M. 



Width of the ilium at the frout of tho aoetabuhiiu 0. 210 



Width of tho ilium at tho posterior expansion 0.200 



Thickness above the acetabulum 0. 0(50 



Width of the acetabulum 0. 105 



Width of the basis of the ischium 0. 0H5 



Wulthof theshaft of arib 0.062 



Other bones, not yet deteniiined, will be iiicliided in the description in 

 the final report. 



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

 restrial saurian s (jr niaramals. / 



HADROSAURUS, Leidy. 



Hadrosaukus mirabilis, 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 lands of Judith 

 River, from which the H. mirabUi-s was procured, tlian 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 

 appearing 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, 0"".060 ; depth of articular face, O^.UTT ; 

 width of articular face, 0"'.071 ; length of base of neural arch, 0™.038. The 

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

 dentalis, although in the opisthocoeliau character it is similar. 



Hadrosaurus occiDENTALis, l^eidy. 



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

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

 caudal vertebra?. Teeth unknown. 



Fra<(ments of a large Dinosaur, from Colorado, were found associated 

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

 which contains the H. occidentaUs (see under head of Cionodon ardatm), and 

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

 parison. 



