ROOM III. TIBIA AND FIBULA OF THE IGUANODON. 



293 



pressed condyles (c, d), which are separated in front and 

 behind by a deep furrow (e). 



Near the middle of the shaft, 

 the mesial or inner edge forms 

 a compressed ridge, which extends 

 into an angular median projec- 

 tion or trochanter (6). 



Thus the upper part of the 

 femur may be recognised by the 

 presence of the outer trochanter 

 (a) and if that be absent, by the 

 fractured surface indicating the 

 position it occupied. If a frag- 

 ment of the middle part of the 

 shaft only is found, the flattened 

 angular spaces, and the sub-me- 

 dian trochanter (6), or the mark 

 of its attachment, will identify it. 

 The lower end may be known by 

 the deep grooves between the con- 

 dyles both in front and behind. 



The medullary cavity is very- 

 large, and generally filled with 

 sandstone : it is sometimes occu- 

 pied by white calcareous spar, 

 spangled with golden pyrites. 



TIBIA AND FIBULA. Wall-case 

 C. (ante, p. 227). The bones of the 

 leg, though presenting deviations 

 from those of the Iguana, mani- 

 fest a close affinity to the lacer- 

 tian type. 4 



The head of the tibia, is subtri- 

 angular, and slightly excavated to receive the condyloid 

 extremity of the femur. The shaft is subcylindrical, and 

 very strong, with a large medullary cavity ; its distal end is 

 transversely oblong and very thick, and terminates on the 

 inner aspect in a strong buttress. 



The iihula is a long slender bone, with a subcylindrical 

 shaft, widest in its antero-posterior diameter ; it is flattened 

 on the tibial aspect, and terminates above in a laterally com- 

 pressed head, which is in close apposition to the tibia \ its 



LIGN. 62. 



1. FIBULA; 2, TIBIA, OF THE 

 IGUANODON. 

 (JL not. tize.) 



