PEOM THE KIMMEPvIKaE CLAY. 451 



form met with in Wealden thigh-bones. The condyles have been 

 much split (iv. 12, 13, 10, 11) into many pieces ; but the deep 

 narrow anterior intercondyloid notch, characteristic of the femur of 

 Wealden Iguanodonts, is plainly recognizable here. The medul- 

 lary cavity was very large ; and the portions of bone referable 

 to the diaphysis show that this was a relatively thin tube of bone 

 enclosing a very large quantity of unossified substance. 



Tibice. — The pieces iv. 5, iv. 6, are the knee ends of the right and 

 left tibise. They show an imperfect condylar division of the gonal 

 surface, and that the praecnemiai crest was remarkably large and 

 strong. The fossil iv. 7, the distal end of the left tibia, agrees 

 essentially in form with the same part in Wealden Iguanodons 

 from the Isle of Wight. The entering angle in the antero-external 

 surface, the salient angle in the postero-internal surface, and the 

 malleolar division of the articular surface into a stouter and shorter 

 inner and a narrower and longer outer half, each having a different 

 aspect adapted to corresponding subdivisions of the proximal surface 

 of the tarsus, are well illustrated by these fossils. 



Tarsus.— This comprises two distinct bones, a larger inner bone, 

 the equivalent of the astragalus (PL XX. figs. 5, 6), and a smaller and 

 outer one, the representative of the calcaneum (PI. XX. figs. 3-6). 



The astragalus agrees substantially with the Wealden form *. It 

 has a somewhat quadrilateral figure. The upper surface is the 

 counterpart of the inner two thirds of the distal articular surface of 

 the tibia as far outwards as the notch in this latter, but not in- 

 cluding what may be conveniently called the outer tibial malleolus. 

 It is divided into two parts, each of a rudely triangular outline. Of 

 these the inner and larger, a wide shallow hollow, looks upwards, 

 inwards, and backwards, whilst the outer division, a deep narrow 

 trough, looks upwards, outwards, and backwards, when the bone is 

 placed in the position it would take if it were articulated with the 

 tibia, and the longer axis of the distal end of this latter were 

 directed from without and behind forwards and inwards, the direc- 

 tion it probably had in progression. 



The under surface of the astragalus forms the larger inner part of 

 a wide articular pulley, convex from behind forwards, and gently 

 concave from without inwards. This trochlear surface rises some 

 distance on the front of the bone. The inner border of the bone is 

 so deep that it deserves to be termed a surface. It is smooth ; its 

 outline is a rude crescent with blunted horns. Of these the pos- 

 terior meets the hinder border of the bone (a thin lip with a down- 

 ward and forward slant) in an angle which underlies the salient 

 posterior angle of the tibia. The anterior surface forms the 

 ascending lip or process, which fits into the retiring angle in the 

 front of the tibia. The inner half of this lip rises gradually ; and the 

 outer falls abruptly. The outer border of the bone, much shorter 

 and much thinner than the inner, is the outer boundary of the 

 narrow trough-like part. Here the upper or tibial and the trochlear 

 surface nearly meet. 



*. See Quart, Jouru. Geol. Soc. vol. xxx. p. 24. 



2h2 



