On a New Spades of Scymnognathus (S. tigriceps). 33 



EADIUS AND ULNA. 



The bones of both sides are present, those of the left being found 

 in sitil in connection with the humerus, and but slightly displaced 

 from their natural positions. 



The radius is 155 mm. in length, expanded at its two ends, and 

 19 mm. in diameter at its narrowest. Proxirnally, the articular 

 surface is elongated slightly in the direction of the ulna, and is 

 slightly concave. It is 50 mm. long and 40 mm. broad. From the 

 proximal end a ridge runs down the ulnar side of the bone ; on the 

 opposite side the shaft is flattened ; so that in section the shaft is 

 markedly triangular at its middle point, with the two anterior 

 angles rounded. The distal articulation is almost circular in section, 

 measuring 40 mm. in diameter, and is convex. 



Only the proximal ends of both ulnae are preserved. The articular 

 surface measures 44 mm. in length and about 37 in breadth. There 

 is no well-developed olecranon process for wrapping round the 

 humerus. Distally, the bone becomes thinner, and 80 mm. from 

 the proximal end has an average thickness of only 11 mm. 



MANUS. 



The manus of the' left side is almost complete, and the bones are 

 preserved in position and in connection with the radius and ulna. 

 We are thus for the first time in a position to give a complete 

 account of the Gorgonopsian carpus, metacarpus, and phalanges. 



The most striking feature of the carpus is its resemblance to that 

 of the Pelycosaurs and its less striking resemblance to that of either 

 the Anomodonts or the Dromasaurians. This manus also sets at 

 rest all doubt as to the Therocephalian digital formula. Formerly it 

 was believed to be 2, 3, 3, 3, 3, but two years ago it was shown by 

 one of us that the formula almost certainly was 2, 3, 4, 5, 3, there 

 being two very short epiphysis-like phalanges in the 4th digit and 

 one short phalanx in the 3rd digit. We now see that this is correct, 

 and that the formula is as in the Pelycosaurs 2, 3, 4, 5, 3, and not 

 as in the Dromasaurians, Anomodonts, and Cynodonts 2, 3, 3, 3, 3. 



The radiale articulates apparently with the whole of the distal end 

 of the radius. Though relatively short it is wide and deep. Distally 

 it articulates with both the centralia, and when the manus is flexed 

 also with the 1st carpal. 



The ulnare is comparatively flat and much longer than narrow. 

 Proximately it articulates with the ulna and the intermedium, and 

 possibly also with a small pisiform. Distally it articulates with the 



3 



