Thecoclontosaurus and Palseosaurus. 161 



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

 pressed aspect on this inferior surface. The condyles are 

 rounded, moderately developed ; the internal condyle is 

 broken. The bone has the usual slight sigmoid curve ; it 

 thickens towards the proximal articulation. The measure- 

 ment from the proximal articular surface to the inferior angle 

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

 humerus of Zanclodon figured by Plieninger 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 

 Stutchbury as the tibia, may be the ulna of Pakeosaurus. The 

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

 identified, and the development of the proximal olecranon 

 process is an approximation to Pai-eiasaurus, which is also 

 found in Stegosaurus (Marsh, Am. Journ. 8ci. vol. xix. 

 pi. viii. fig. 3). 



Distal end. 



Lateral aspect of the ulna. Brist. Mus. no. 46. -\ nat. size. 



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

 and posterior outlines, lyV inch wide, with the distal end 

 convex from front to back, without 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 

 the Saurischian ulna, with the articular surface inclined to 

 look upward and forward. There is a wide compressed 



