CRETACEOUS FORMATIONS. 49 



but also in the absence of the compressed process which projects from the inner side 

 of the middle of the shaft. The bone also expands more gradually than in the femur 

 of the Iguanodon, and the posterior part of the condyles must have been wider apart 

 in consequence of the posterior inter-condyloid longitudinal excavation being longer 

 and wider. The middle part of the shaft of the femur is subcompressed, with a 

 nearly quadrilateral contour of the transverse section, the line bounding the outer 

 side being less convex and longer than that which circumscribes the inner side of the 

 bone : the anterior surface is flatter than the posterior one. The anterior and outer 

 surfaces meet at a more marked angle than do any of the others ; the angle being 

 formed by an obtuse ridge. The concavity of the posterior surface begins about 

 6 inches above the broken distal end of the present fragment, and gradually increases 

 in both width and depth as it descends. The width of the inter-condyloid groove at 

 the fractured distal end is 5 inches 4 lines. The same admeasurement in the largest 

 Iguanodoiis femur gives 2 inches. The convex ridge leading to the inner condyle is 

 more prominent than the outer one ; and on the tibial side of the inner ridge there is 

 a second slight concavity. On the anterior surface of the distal end of the femur 

 there is a broad shallow depression of the surface, corresponding to the deeper one 

 behind, and there is not the narrow and deep groove which characterises the corres- 

 ponding part of the femur of the Iguanodon. The texture of the distal end of the 

 bone presents the same coarse cancelli as occupy the middle of the upper part of the 

 shaft, but with a thinning of the outer laminated compact crust. The following 

 are admeasurements of the bone not given in the above description : — 



Transverse diameter of the middle of shaft .... 

 Antero-posterior or lesser diameter of ditto .... 

 Greater diameter of the distal end . 

 Smaller diameter of ditto at middle of the inter-condyloid groove 



Tibia and Fibula. — The portion of a tibia, T. XIII, fig. 1, t, which has been pre- 

 served, is compressed near its head, and the side next to the fibula is slightly concave. 

 The longest transverse diameter is 8 inches 9 lines, and the two other transverse 

 diameters at right angles to the preceding give respectively 3 inches 3 lines, and 

 2 inches 6 lines. The bone soon assumes a thicker form, its circumference at about 

 one third from its proximal end being 16 inches 6 lines. The compact laminated 

 outer wall of the bone is 4 lines thick. The cancelli occupying the central portion of 

 the bone are arranged in a succession of layers around a point nearest the narrower 

 end of the transverse section. Lower down the tibia again becomes compressed, and 

 towards the distal end the transverse section exhibits the form of a plate bent towards 

 the fibula, and its narrowest transverse diameter is 1\ inches. 



The portion of the fibula, T. XIII, fig. 1,-f, is ll£ inches long. In the middle it is 

 flat on one side, slightly concave on another, and convex on the two remaining sides. 



Inches. 



Lines, 



5 



6 



3 



9 



12 







5 







