Tliecodontosauius and Palasosaurus. 161 



concavity above tlie distal condyles, and the bone has a com- 

 pressed aspect on tiiis inferior surface. The condyles are 

 rounded, moderately develojied ; the internal condyle is 

 broken. Tlie bone has the usual sliyiit sigmoid curve ; it 

 thickens towards the proximal articulation. The measure- 

 ment from the proximal articular surface to tlie inferior angle 

 of the radial crest is 3j"^,, inches. This bone is similar to the 

 humerus of Zanclodon figured by Plieningcr in all its cha- 

 racters, except that its radial crest appears to have a rather 

 greater transverse width. 



Ulna. (Fig. 10.) 



A specimen, no. 46 (fig. 10.), originally figured by Riley and 

 Stutehbury as the tibia, may be the ulna of Paheosauras. The 

 absence of curvature in the bone is not opposed to its being so 

 identified, and the develo))ment of the proximal olecranon 

 process is an aj^proximation to Pareiasaurus, wliich is also 

 found in Stegosaurus (Marsh, Am. Journ. tSci. vol. xix. 

 pi. viii. fig. 3). 



Fig. 10. 



Proximal end. 



Distal end. 

 Lateral aspect of the ulna. Brist. Mus. no. 46. ; nat. siize. 



The ulna is about 4/^ inches long, concave on the anterior 

 and posterior outlines, It'ij inch wide, with the distal end 

 convex from front to back, witliout sign of excavation of the 

 distal end. 



The proximal end is 1^ inch wide, with the articular 

 surface slightly concave from front to back, margined by a 

 distinct anterior edge like that seen in other examples of 

 tiie tSaurisehian ulna, with tlie articular surface inclined to 

 look upward and forward. There is a wide compressed 



