FAUNA OP THE GOSAU FORMATION. 



657 



of i ts inferior border from, the humeral articular surface is between 

 6 and 7 centim. From the inferior margin of the acromion descends 

 a strong rounded ridge which divides the part of the bone above the 

 humeral articulation into anterior and posterior areas, and, but for 

 the intervening acromion process, would look like a continuation of 

 the spine. This ridge dies away before reaching the humeral arti- 

 culation. Posterior to the acromion the surface of the scapula is 

 broadly channelled. In its singular curvature and development of 

 the acromion it is unlike the scapula of any other Dinosaur. 



The second specimen, though evidently belonging to the same spe- 

 cies, is a little smaller ; it has been reconstructed out of even a larger 

 number of fragments than the specimen described. The proximal 

 part of the bone is wanting, the fracture having removed the arti- 

 cular region and acromion process ; but this portion was compressed 

 from side to side ; the anterior margin of the bone, however, appears 

 to be thicker, and the cavity in front of the acromion is more 

 marked, than in the specimen here figured. Distally a portion of the 

 terminal free margin of the bone is preserved, showing that it was 

 obliquely truncated and somewhat thickened and roughened with 

 muscular attachments, especially towards the posterior border ; the 

 specimen, as preserved, is 27 centim. long and about 76 millim. 

 wide in the blade, where it is widest. The details of the two bones 

 otherwise present the closest agreement. 



Distal End of Humerus. 



A large humerus is unfortunately only known from its distal end 

 (PI. XXIX. fig. 4), which has decayed in the manner so frequent 

 with these fossils, and as though indicating that the terminal end 

 had been a distal epiphysis similar to that which characterizes the 

 long bones in the order Sauropterygia, which may have separated 

 from the shaft absolutely or decayed in consequence of the less per- 

 fect ossification of its cartilaginous substance. 



This fragment is little more than 4 inches long. It exhibits at 

 the proximal end a natural fracture, made during extraction from 

 the rock ; and here the bone is 1^ inch thick, ly^- inch wide, ovate 

 in outline, with an angular bulge towards the middle of the superior 

 surface — a bulge which indicates a ridge similar to that referred 

 to in the more perfect specimens of the other species (PI. XXIX. 

 fig. 1). I regard this specimen as the distal half of a left humerus 

 of Cratceomus Paivloivitscliii. 



The fracture is somewhat interesting as showing the existence 

 of a central medullary cavity (PI. XXIX. fig. 5). This cavity is 

 y 7 ^ inch long and more than | inch wide ; so that the bone round 

 it is about half an inch thick ; and this contrasts remarkably with 

 the thinness of the terminal and irregular edges of the distal margin 

 of the shaft, which is nowhere much more than y 1 ^ inch thick, though 

 becoming somewhat thicker as it extends proximally. The cavity 

 is relatively smaller in the second species. The superior surface is 

 unfortunately somewhat crushed ; and the whole specimen has been 

 pieced together, like so many of these remains, with great patience, 



Q.J.G.S. No. 148. 2x 



