54 



rest on the ilium; the posterior pair the most expanded; the superior mar- 

 gins of its posterior edge form an open V, with the apex forward on the 

 neural arch of the fifth vertebra. On the last sacrals, the diapopbyses rise to 

 the neural arch again. The exits of the sacral spinal nerves are behind the 

 middles of the centra, and continue into grooves of the sides in all but the 

 last vertebra?. The reduced and rather elongate form of the last sacral verte- 

 bra induces me to believe that this animal did not possess such large and 

 short caudal vertebras as are found in the genus Hadrosaurus, and that the tail 

 was a less massive organ. 



The. ilium is much more elongate than the corresponding element in 

 Hadrosaurus, Cetiosaurus, or Megalosaurus. Its upper edge is turned and 

 thickened inward above the anterior margin of the acetabulum, and here the 

 middle of the conjoined diapophyses of the second and third sacral vertebrae 

 was applied when in place. In front of this point, the ilium is produced in 

 a straight line and a stout flattened form with obtuse end. Posterior to it, its 

 inner face is concave to receive the second transverse rest of the sacrum, and 

 the superior margin is produced horizontally toward the median line like the 

 corresponding bone in a bird. The posterior part of the bone is the widest; 

 for it is expanded into a thin plate and produced to a considerable length. 

 From one of the margins (ray sketch, made on the ground, represents it as 

 the upper), a cylindric rod is produced still farther backward. This it is 

 believed is only the shaft of a displaced rib. The base of the ischium is co- 

 ossified with the ilium, and is separated behind its base from the iliac portion 

 of tin 1 acetabulum. There is no facet nor suture for the pubis at the front 

 of the acetabulum. 



The ribs are compressed. There are no bones certainly referable to the 

 limbs. 



The form of the ilia distinguishes this genus from those known hereto- 

 fore. 



Agathaumas sylvestris, Cope. 



Proceedings of the American Philosophical Society, 1872, p. 482. 



The last nine dorsal vertebrae have rather short centra; the most poste- 

 rior the shortest. They are higher lhan wide; the sides are concave, the in- 

 ferior face somewhat flattened. The neural arch is keeled behind from the 

 canal to between the posterior zygapophyses, and a similar keel extends from 

 the base ol* t he neural spine to between the anterior zygapophyses. The 



