20 



HADROSAURUS OCCIDENTALIS. 



Cope; Extinct Batracbia, etc., p. 98. Thespesius occidentalism LiiiAj. 

 Proceedings of the Academy, Philadelphia, 1856, p. 311. Transactions 

 of the American Philosophical Society, 1860, p. 151. 



Prom the lowest member of the lignite formation at Grand Kiver, Ne- 

 braska. 



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

 Thespesius^ on account of the slightly opisthocoelian character of the 

 large caudal vertebra. 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. occidentalism (see under head of Cionodon 

 arctatus,) and may possibly belong to it. 1 have no identical parts in 

 the two for comparison. 



Char, specif. The largest fragment of a long bone is probably from 

 the proximal end of the tibia ; it includes the curved inner border of the 

 Bide, and the inner posterior tuberosity, with five inches of the inner 

 head side of the shaft. The superficial layer is marked with num- 

 erous closely-placed longitudinal groo^^es, which are replaced by a few 

 coarser and deeper ones which interrupt the anglewith the articular 

 surface, giving it a lobate margin. There was probably a prominent 

 cnemial crest. Another fragment exhibits one flat plane, and a concave 

 posterior face. It comes from near the extremity of humerrus or femu; 

 it was found near the fragment of tibia. The sacral vertebra is prob- 

 ably that of an animal not fully grown, as it was not co-ossified with 

 those adjacent. The articular extremities are expanded, and present 

 distinct faces for articulation for the large diapophyses. The one ex- 

 tremity is more expanded and less thickened ; the other more thickened 

 and less dilated : on this rests the greater part of the base of the neural 

 arch. Just at the extremity of this base the large sacral nervous for- 

 amen issues, which is continued in a wide groove downward between 

 the transverse expansions. Inferior surface convex. As compared with 

 the fourth sacral vertebra of Agatliaumas sylvestriSj Cope, which it nearly 

 resembles in size, it is to be observed that the anterior extremity is less 

 expanded transversely as compared with the posterior; that the bases 

 of support for the anterior diapophyses are not produced downward so 

 far ; that the sides of the centrum are nearly vertical and not sloping 

 obliquely toward the middle line ; and that there is no inferior plane 

 separated from the lateral by a longitudinal angle, as in A. sylvestris. It 

 differs in like manner from the third and second sacral vertebrse, and 

 still more from the first of the latter saurian. 



Measurements. 



M. 



Length centrum of fourth sacral vertebra 092 



( in front 103 



Transverse diameter ) at middle 072 



( posteriorly 121 



Vertical diameter posteriorly 092 



Diameter head of tibia antero-posteriorly 250 



Hadrosaurus agilis. Marsh. 

 Amer. Journ. Sci. Arts, 1872, p, 301 



From the Niobrara or Cretaceous, No. 3, of Western Kansas. 

 Smaller than the preceding species. 



