FAUNA OF THE G0SAT7 FORMATION. 



687 



face was presumably convex from side to side, though (owing, I think, 

 to crushing) it has a longitudinal groove. There is a small muscular 

 tuberosity on the outer anterior margin, as in the Alligator, just 

 where the compressed and curved proximal end merges into the 

 straight and nearly cylindrical shaft. The shaft at the fracture is 

 7 millim. long by 6 millim. wide, and has a medullary cavity 

 which is over 2 millim. in diameter (fig. 11). 



Ulna. 



With the radius figured by Biinzel, pi. vii. figs. 7, 8, occurs an 

 ulna. The radius was regarded as that of a lizard. The ulna, which 

 is slender and compressed, with a somewhat expanded proximal end, 

 is exactly paralleled by some of the living short-snouted Crocodiles. 

 The ulna (PI. XXIX. figs. 9, 10) is 6 j centim. long, and referable to the 

 left side of the body ; it has the shaft smooth, compressed from side 

 to side, and contracting and curving as»it descends from the humeral 

 to the carpal surface. The articular head of the bone (fig. 10) is 

 remarkably large, being in antero-posterior measurement over 17 

 millim., while the width is 11 millim. towards the radial border, and 

 about 1 centim. at the posterior border. This surface is somewhat 

 concave from front to back. Immediately below the articulation at 

 the proximal end is a deep impression, which may possibly be due 

 to pressure, but may also indicate the entrance of a large vessel into 

 the bone. On the superior aspect there are natural impressions in 

 the middle of the side and below the inner margin of the articular 

 surface. The thickness of the shaft just below the articular head is 

 5 centim. ; and though this thickness becomes reduced a little in the 

 middle of the shaft, there is a slight thickening again towards the 

 distal end. The width of the shaft just below the articulation is 

 1 centim.; and this width diminishes to about 6 millim. just above the 

 distal articulation. On the superior surface of the distal end of the 

 shaft a ridge appears at the hinder margin, which extends obliquely 

 across the bone. The distal end is a little crushed and twisted, sub- 

 reniform, more than 1 centim. wide, and 6 millim. thick, and makes 

 an angle of about 45° in the plane of its direction with the proximal 

 end. The form of the articulation appears to include three regions — 

 first a deep middle groove, external to which is a small spherical 

 ball, while internal to it is a concavity. The median groove and the 

 compression of the bone on the inferior margin give to the articula- 

 tion somewhat of a broad Y-shape. 



Radius. 



The radius is represented by both right and left bones. The speci- 

 men figured by Biinzel (pi. vii.figs.7, 8) appears to me to be left. It is a 

 straight bone, 6*2 centim. long, corresponding in length with the ulna. 

 The proximal end (PI. XXIX. fig. 13) of the bone is expanded trans- 

 versely, with a thickened margin on the inferior border. This end of 

 the bone is fully 1 centim. wide, but, as preserved, is only \ centim. 

 thick, probably owing to crushing of the superior articular border. 



