214 THE BATH OOLITE PERIOD. CHAP. 



In the large femur from Enslow rocks we may take the length, 

 when complete, at thirty-six inches ; at thirteen inches down the 

 bone the lesser trochanter begins, and it extends six inches. 



The femur is, or appears to be, internally hollow, quite clear of 

 structure like a bird's bone. 



The tibia of megalosaurus is shorter than the femur in the 

 proportion of twenty-seven inches to thirty- three ; it is compressed, 

 especially in the distal half, and has in the upper part, in front, 

 a prominent procnemial ridge, somewhat like that of a struthious 

 bird. On the outer edge, one-fourth of the length downward, is 

 a rough exocnemial crest for the coherence of the fibula. The 

 head of the bone is longer than broad, oval in outline, and narrowed 

 toward the procnemial crest. It is somewhat depressed across, and 

 has on the outward edge the marks of the attached fibula. 



Viewed in its general relations, the tibia appears a nearly straight 

 bone ; it is, however, in a certain degree twisted, being much 

 compressed from front to back in the lower part, and in a less 

 degree from side to side in the upper part. If it be viewed length- 

 ways, the articular ends lie in such a manner that their outlines 

 cross one another nearly at right angles, as Professor Huxley has 

 remarked. 



The lower end of the tibia is peculiar in the mode of articulation 

 with the astragalus. For that bone, instead of being as usual partly 

 posterior, and occupying the whole breadth of the tibia, rises up- 

 ward in front in a broad flat plate, which fits to a well-defined 

 hollow on the flattened face. Its extension toward the fibula is cut 

 off in that direction by a nearly vertical surface, which is marked 

 by the attachment of the calcaneum, as Cuvier observed on a 

 specimen from Honfleur (Ossem. Fossiles, Plate XXI. fig. 35). 



On comparing this bone with that of a crocodile, several dif- 

 ferences appear. In that animal the proximal tibial articulation, 

 including the fibular head, makes a transversely oval surface, the 

 outline slightly excurrent in front, of the same breadth as the 

 femoral condyles, and with only a trace of procnemial ridge. The 

 fibula is not attached to the tibia except at the upper edge ; the 

 lower end is convex in front, and much concave behind. The 

 astragalus projects behind, and rises there to a broad articulation 

 with the interior condyle. If these bones of megalosaurus were 

 turned round 180, they would more resemble the arrangement 



