LIASSIC DINOSAURS. 91 



Mr. Harrison the lower half of a right femur and the upper half of the right tibia 

 and fibula, cemented by the matrix in the natural relative position in which they 

 enter into the formation of the knee-joint, when bent. This remai-kable specimen 

 indicates the tranquil state of the sea-bed or bottom after it had received the 

 dead carcass of the Dinosaur. No agitation or other external violence had 

 displaced the bones of the leg after the solution of the ligaments which tied 

 them together in the living animal ; when the depth to which they had sunk, 

 and the consistency of the mud or clay bed, tended to retain them in their 

 natural position. The portion of femur preserved indicates a slight backward 

 bend of the shaft, which at the fractured part — probably a little below the 

 middle of the bone — presents an almost circular transverse section. The 

 circumference here is 10 inches ; the compact wall of the bone is 6 lines 

 thick ; the medullary cavity 2 inches in diameter. A little below the fractured 

 end, and 8 inches above the lower end, the shaft shows the termination of the 

 characteristic inner process. From this point the femur expands gradually, 

 and chiefly in the transverse direction. Posterioi'ly it becomes impressed by 

 the popliteal cavity, which deepens and widens to the upper and back part of 

 the inner condyle ; which, by its production towards the outer condyle, contracts 

 the lower end of the popliteal cavity transversely. On the outer side of the distal 

 expansion of the femur the external wall is in part broken away ; but a shallow 

 and narrow longitudinal impression is indicated, terminating below in a rather 

 shallow notch, which marks out the inner and hinder part of the outer condyle 

 from the outer part of the same condyle. This notch corresponds with that 

 between the tibia and fibula, and defines the portions of the outer condyle 

 assigned to those bones respectively. The inner condyle is rather flattened 

 on the inner side. The tibia is much expanded at the proximal end, chiefly 

 by an extension of the bone forward; it is slightly convex on the inner or 

 tibial side; a longitudinal prominence extends from the fibular side of the 

 expansion, near the fore ipart, answering to the ectocnemial process in the 

 bird's tibia ; the main expansion forms the procnemial process which has subsided 

 to the ordinary level of the shaft about six inches down the bone. The back part 

 of the proximal end of the tibia presents two almost hemispheric protuberances, 

 side by side ; they might be mistaken in a detached bone for the backwardly 

 projecting condyles of a femur, but are less deeply severed. The outer tuberosity 

 articulates with a slight depression in the contiguous part of the fibula. The fore 

 part of the proximal portion of the tibia is, transversely, concave, exterior to 

 the pro- and ectocnemial processes. The fractured part of the shaft, eleven inches 

 below the knee-joint, presents a full, oval section, with the same proportion of 

 compact bony waU to medullary cavity as in the femur ; the white spar filling the 

 cavity contrasts strongly with the jet-black colour of the petrified bone. The 



