570 BRITISH FOSSIL REPTILES. 



Varanus, not tlie larijest, as iu Crocodilas, in which it is connate with the trapezium and 

 trapezoides. 



The proximal surface for the radius is more uniformly and less boldly convex ; the 

 opposite articular surfaces for the trapezium and luuare is more deeply concave. The 

 outer (ulnar) surface is elongate, narrow, and is the smallest on the bone ; it seems 

 barely to have touched the cuneiform, which is here, as in Varanus, the largest of the 

 carpals. 



The free broader radial surface of the scaphoid is flattened and roughened, and seems 

 to have continued, distad, the corresponding surface of the radius itself, which is on the 

 radial side of the distal end of that antibrachial bone (PI. 70, fig. 8, 9). 



The length (transverse extent) of the scaphoid is 5 inches ; the extreme (ancono- 

 palmar) breadth is 3 inches ; the extreme proximo-distal extent (on the rough flat 

 surface) is 1 inch 1 lines. 



The cuneiform is a massive cuboidal bone, with a proximal surface less concave for 

 the ulna than in Varanus, but with as deep an opposite (distal) concavity for the division 

 of the unciforuie which supports the fourth digit. There is an approach to the croco- 

 dilian character of the bone in the increase of the distal part or surface. The transverse 

 extent of the bone there is 4 inches 9 lines ; that of the proximal surface being 

 4 inches ; the ancono-palniar diameter of the bone is 3 inches 9 lines ; the proximo- 

 distal diameter is 3 inches 10 lines. 



The unciform seems, as in the Crocodile, to have supported both fourth and fifth 

 metacarpals, not to have been divided to afford articulations for these bones on separate 

 portions. Its transverse extent in Omosaurus is G inches 4 lines ; the other dimensions 

 closely correspond with those of tlie cuneiform carpal. 



The digits of a hind foot are longer, as a general rule, than those of a fore foot in 

 existing Saurian Reptiles, and the same proportion has been demonstrated in the fore and 

 liind feet of some extinct Dinosauria.* The proportions, at least, of the metatarsals in 

 HylcEosaurus and Scelidosaurus support a belief that tiiose of the metacarpals would be as 

 in the homologous bones of Itjuanodon. 



Of the five metapodial bones of Omomiints which have been wrought clear out of the 

 matrix not any show a length as compared with the breadth which exceeds that of the 

 metacarpal of the first digit in the fore-foot of Jgitanodon (' Dinosauria' PI. 48, fig. 1, »«) ; 

 and the homologues of the intermediate metacarpals are shorter in proportion to their 

 l)readth than in Iguanodun. 



I conclude, therefore, that the above metapodials of Omosaurus are metacarpals, that 

 the digits were less unequal in length, and the whole fore-foot was more massive and 

 elephantine in its proportions, in Omosaurus than in Iguanodon. 



A metacarpal {' .Dinosauria,' PI. 71, figs. 3 — 6) has a flattened proximal surface (ib., 

 fig. 5) of a subtriangular shape, slightly convex near its radial [r) and anconal [a) peri- 

 * Jymmodon, ' Dinosauria,' PI. 45 ; Ilijheosaurus, ' Dinosauria,' PI. 44 ; Scelidosaurus, &c. 



