4 FOSSIL REPTILIA OF THE 



the lower end, the shaft shows the termination of the inner process. From this 

 point the femur expands gradually, and chiefly in the transverse direction. Pos- 

 teriorly 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 (a). The tibia is much expanded at the proximal 

 end, chiefly by an extension of the bone forward (fig. 1); it is slightly convex on 

 the inner or tibial side (<?) ; a longitudinal prominence extends from the fibular side 

 of the expansion, near the fore part, answering to the ectocnemial process in the 

 bird's tibia ; the main expansion forms the procnemial process (figs. 1 and 2,p) 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 (fig. S) presents two almost hemi- 

 spheric protuberances (fig. 3, c , d), side by side ; they might be mistaken in a de- 

 tached bone for the backwardly projecting condyles of a femur, but are less deeply 

 severed. The outer tuberosity (rf) articulates with a slight depression in the con- 

 tiguous part of the fibula (/). The fore part of the proximal portion of the tibia is, 

 transversely, concave, exterior to the pro- and ecto-cnemial 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 wall to medullary cavity as 

 in the femur ; the white spar filling the cavity (m) contrasts strongly with the 

 jet-black colour of the petrified bone (*'). The transverse diameter of this part 

 of the shaft is 2 inches 3 lines ; the fore and aft diameter is 2 inches 6 lines. 



The fibula expands chiefly in the fore and aft direction at its upper end 

 (fig. 2,^), where it measures 5 inches across. Six inches lower down this diameter 

 has contracted to one of 1 inch 8 lines ; eleven inches lower it measures 1 inch 

 3 lines, the transverse diameter being 9 lines. Seven inches from the proximal 

 end the fibula presents at its outer and back part a thick, longitudinal, rough ridge, 

 for the attachment of a muscle. It continues in contact with, and gets rather 

 behind, the tibia as it descends. 



