FAUNA OF THE GOSATJ FORMATION". 



659 



of an inch ; it originates distally in the part of the shaft which is most 

 constricted, runs rather nearer to the external than to the internal 

 margin, and increases in strength proximally till it becomes T 2 ^ inch 

 wide, where the shaft is 3 inches in diameter. All that part of the 

 shaft which is external to the ridge is obliquely flattened, with a 

 slight increase of inflation towards the proximal end, but without the 

 slightest indication of the formation of a proximal trochanter, which 

 presumably was not developed, though the absence of this struc- 

 ture may be due to mutilation. The inner side of the shaft is rather 

 more convex than the outer side ; but on its upper side there curves 

 round from where the lateral trochanter should be, a muscular ridge, 

 which is rather stronger but less well denned than the principal 

 median ridge, towards which it very slowly converges proximally. 

 At first the width between the ridges is nearly 1| inch : but at 

 3 inches nearer to the proximal end it is narrowed to 1^ inch ; and 

 as it narrows, the area thus defined between the muscular ridges, 

 which is at first fiat, becomes very markedly concave. Proximally 

 the bone curves inward as though approaching the terminal arti- 

 cular head, and the space external to the inner ridge is fairly well 

 rounded. The proximal half of the posterior aspect of the bone is 

 somewhat crushed, and appears to have been more convex than 

 usual. It may have terminated towards the outer side in a slight 

 ridge, and shows but very slight or uncertain indications of the 

 posterior muscular ridge seen in the second species. The lateral 

 trochanteroid muscular indication is placed a little higher up than 

 is usual with the lateral trochanter ; it is about 1^ inch long, slightly 

 elevated and rounded; its proximal end inclines slightly towards 

 the anterior face of the bone. The lateral outline of the bone is 

 here markedly convex. 



The distal end of the bone gives no indication of the widening 

 on the outer side of the articulation which is so often met with, 

 since it is flattened and straight externally. Posteriorly there is 

 a moderately deep broad channel inclined a little outward ; it was 

 evidently prolonged between fhe condyles, and shows the outer 

 condyle, as usual, to have been small, while the inner condyle was 

 large. The bone appears to have been quite as much thickened as 

 usual at the distal end, though only the backward curve of the shaft 

 and no part of the articulation itself is preserved. The whole sur- 

 face of the shaft is remarkable for the longitudinal muscular rough- 

 nesses, which are more marked than in any reptile bone that I have 

 ever seen. 



Tibia. 



Apair of large limb-bones, both 8 inches long, as preserved, but muti- 

 lated before fossilization, so that no trace is shown of either proximal 

 or distal articulations, present, however, characters which unmista- 

 kably show them to be the tibial bones (PI. XXXI. fig. 2). The frag- 

 ments are straight on the inner side. The shaft bends inward a little at 

 the distal end, has a long anterior crest immensely developed forward 

 at the proximal end, and sends out a compressed process on the outer 



2x2 



