peer OkeE LEG: AND’ PECTORAL’ GIRDLE 
OF MOROSAURUS. 
By E. S. RIGGS. 
The genus Morosaurus* Marsh, is based upon a sacrum offering 
for its primary distinguishing character the presence of four codssified 
centra. Other distinguishing characteristics are the massiveness of 
the anterior portion of the skull and mandible, the expansion of the 
upper end of the scapula, the broad blade of the ischium and the poste- 
rior direction of its distal end. The sutural articulation of the neural 
arch with the centrum in the vertebre is not significant but dependent 
upon age. 
Marsh has proposed five species under this genus: MW. grandis, 
M. impar, M. robustus, M. lentus and M. agilis. Of these species he 
offers but few distinctive characteristics and in his monograph makes 
no attempt to distinguish them. JM. zmpar was the type of the genus, 
but, as Williston has already pointed out,f it is clearly a synonym of 
M. grandis earlier described as Apatosaurus grandis. While the speci- 
men upon which the former species was based must remain the 
generic type, that of the latter being much more complete and better 
known will naturally be referred to in comparisons. M. robustus is 
based upon a lone ilium larger than the last, but otherwise difficult to 
identify. MZ. /entus is not to be distinguished by the sutural articula- 
tion between the centrum and the neural arch of the vertebre as 
Marsh’s figures would suggest, but by the massiveness of all parts of 
the skeleton and the depression of the vertebral pedicles so that the 
neural arch rests directly upon the centrum. ‘The suture is notice- 
able in young specimens of other species and evidently disappears in 
the adult. M. agilis, in direct contrast with the last named species, 
is characterized by the lightness and slenderness of its skeleton and 
by its very small size. In the hind foot the first digit is massive 
while the other four are unusually slender. 
The genus Morosaurus is represented in the collections of this 
Museum by a nearly complete fore leg with coraco-scapula, two other 

*American Journal of Science, 3d ser. Vol. XV, p. 242. 
Kan. Univ. Quarterly, Vol, VII, p. 173. 
275 
