100 PROCEEDINGS OF THE ACADEMY OF [1883. 



duced calcaneum, which supports the extremity of the fibula. 

 There are four digits of the anterior foot, and three of the pos- 

 terior. The fore-limb is much shorter than the hind-limb, so that 

 the attitude of the animal was kangaroo-like, as in Hadrosaurus 

 and Laelaps. In this it differed from Monoclonius,^ where the 

 anterior limbs are as long as the posterior. 



Ordinal Characters. — The quadrate bone is immovably articu- 

 lated to the skull by three elements ; the parietal, the quadrato- 

 jugal, and the jugal. The intercalare occupies a position on the 

 external edge of the exoccipital, and nearly approaches the 

 proximal end of the quadrate at its* posterior side. The post- 

 frontals and prefontals are well developed, and the parietals, 

 frontals, nasals and premaxillaries form the middle line of the 

 skull above, as in other reptiles. The elements of the lower jaw 

 belonging to reptiles are all present. 



Subordinal and Fawily Characters. — The parietal is, as to its 

 superior face, a T-shaped bone, of which the transverse portion 

 rests on the supraoccipital bone, without interspace. The external 

 extremities of the transverse branches are excavated below to 

 ]-eceive the proximal end of the quadrate. These extensions of 

 the parietal are stout, and represent the parietosquamosal arch 

 of the Lacertilia. Resting as they do on the occipital, the}" present 

 a character exactly intermediate between those presented by the 

 Crocodilia and Lacertilia. 



The zygomatic arch is complete, having the usual flexure observed 

 in reptiles, and branching to a postorbital arch by the interven- 

 tion of a postorbital bone. The postorbital part of the 2;ygomatic 

 arch forms the external border of the superior aspect of tlie skull, 

 and encloses a crotaphite foramen. The portions of the frontal 

 and parietal bones which separate the crotaphite foramina, form 

 a narrow isthmus. The postorltital part of the zygoma consists 

 chiefly of the squamosal. This element is rod-like, and does not 

 reach or take part in the articulation with the quadrate. In this 

 respect this genus differs materially from Scelidosaurus, where, 

 according to Owen, the squamosal is more extended posteriorly, 

 and articulates with the superior part of the quadrate by a fixed 

 articulation. The external portions of the parietal are thus, in 

 Scelidosaurus, correspondingly reduced. 



The malar or jugal bone is of large size, while the quadrato- 



' Proceedinors Phila. Academy, 1876, Optoibei;'. 



