12 



I describe here a humerus which I suppose to belong to one or the other of these 

 large species. The great tuberosity is of huge dimensions, exceeding in anteroposterior 

 diameter the head and lesser tuberosity together. Its external face forms a triangular area 

 which terminates at its inferior apex in a large compressed process which is directed out- 

 wards. Below this the smooth surface of the shaft winds spirally from a posterior posi- 

 tion to the front, where it is bounded below by a narrow, deep, transverse coronoid fossa. 

 It is bounded externally below by a ridge which is produced upwards from the internal 

 epi condyle in a short tuberosity. The olecranar fossa is very deep and has abrupt sides. 

 The external epicondylar region is flat. 



Measurement of Humerus. 



Mm. 

 Length 460 



' of entire head 210 



Anteroposterior diameter 1 



■r 



(. of condyle only 110 



f of head 158 



Transverse diameter-! 



(of condyle 93 



{Anteroposterior 80 

 Transverse 72 



f Transverse 130 



Diameter of distal condyles -J ( External 98 



I Anteroposterior -1 



L (.Internal 72 



Distal width, with epicondyle 150 



I compare the only entire femora in the Cypress Hills collection with one nearly entire 

 from Colorado in my collection. The latter was found near other bones which belong pro- 

 bably to the M. americanus, and the Cypress Hills specimen not improbably belongs to the 

 M. proutii. The head and condyles are smaller than those of the M. americanus. The 

 great trochanter extends as far proximad as the line of the head, while it falls consider- 

 ably short of it in the M. americanus. The third trochanter is not prominent, but forms 

 the inferior extremity of the wide proximal two-fifths of the bone, a slight concavity of the 

 external border existing between it and the great trochanter. Below it the shaft is abruptly 

 contracted on the external side. It then expands equally on each side to the condyles, 

 giving the posterior face a wide, slightly concave face proximad to the latter. Their 

 articular surfaces are continuous with each other, and with that of the rotular surface, at 

 the point of junction of which their external borders are notched. The rotular groove and 

 its lateral ridges are injured. Enough remains to show that there is a fossa at its prox- 

 imal border on the shaft. The inferior part of the femora of the M. americanus does not 

 differ except in its superior dimensions. The following are the measurements : — 



Measurements of Femora. 



M. proutii. M. americanus. 

 Mm. Mm. 



Length 6 00 



Anteroposterior diameter of head 90 119 



Width at great trochanter 187 182 



" third " 115 



" (least) below third trochanter 76 96 



" above condyles 150 180 



" of condyles 125 150 



Anteroposterior diameter (least) below third trochanter 55 CO 



