300 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



27 inches. The greatest thickness of the wall of the shaft 

 is 2 inches; the diameter of the medullary cavity 5 inches 

 by 3. In all the femora which I have examined, the medul- 

 lary canal extends from above the condyles to within one- 

 third of the top of the bone. 1 Of the right femur, which 

 from its correspondence in size is probably referable to the 

 same individual as the left, two large portions of the shaft 

 were alone obtained. Now, if we take as a scale of propor- 

 tions the large femur in the Walkcase 0, the bone above 

 described, if perfect, would be of the following dimensions : 



Total length 4 feet 8 inches. 



Circumference of the head exclusive of the outer 



. v trochanter 3 2 



the shaft at the base of the 



middle trochanter 2 1 



the distal end round the condyles 3 6 



" A tibia found with the above, consists of about two-thirds 

 of the shaft, with the distal or tarsal extremity nearly entire ; 

 it measures as follows : 



" Length along the middle of the shaft 27 inches. 



Length to the distal inner process 32 



Circumference of the distal or tarsal end .... 25 



middle of the shaft .... 18 



upper part 20 



Probable length of this tibia when perfect, 4 feet. 



" A fragment of the shaft of another tibia is 23 inches in 

 circumference ; and the distal end of one from Sandown Bay 

 27 inches. 



"As a contrast to these gigantic remains, bones of the 

 extremity occasionally occur so small, yet so compact, as to 

 suggest the probability that they may belong to distinct 

 species; but at present I have not been able to detect other 

 characters which would warrant such an inference. A left 

 femur in my possession, from Rusper in Sussex, is 14 J inches 



1 " In this enormous bone the interna.1 structure is beautifully pre- 

 served ; sections properly prepared exhibit the peculiar form and pro- 

 portions which Mr. Bowerbank considers to be characteristic of the 

 reptilian type. That eminent microscopic observer has kindly favoured 

 me with his measurements of the bone-cells in portions of this femur. 

 The general average of the proportions of the length and diameter of 

 the cells is as one to eleven ; the length being -^^ and the diameter 

 th of an inch." 



