116 BRITISH FOSSIL REPTILES. 



The metatarsal of the first or innermost toe (Pis. 57 and 58, i), is 2 inches 9 

 lines long. With its proximal end laterally compressed, and abutting against the 

 corresponding end of the second metatarsal, which is much expanded in that 

 direction. The distal end of the first is 13 lines in breadth, with a convex articular 

 surface. The first phalanx of the toe (») is 2 inches long, 14 lines across the base, 

 convex transversely towards the dorsum of the foot, flattened transversely and 

 slightly concave lengthwise, towards the sole. The ungual phalanx is 1^ inch in 

 length, and 1 inch in basal breadth; is sub-depressed, and curved downward. 

 About 3 lines in advance of the joint, its breadth is increased by two lateral ridges. 

 The apex is subacute. The under surface is marked by many fine, wavy ridges. 

 There are two obtuse longitudinal prominences on the under surface near the joint, 

 for the advantageous insertion of the flexor tendons, and there is a rough prominence 

 at the middle of the dorsal surface, near the joint, for the insertion of the extensor 

 tendon. The dorsal surface near the margins and apex, is sculptured by vascular 

 grooves. The total length of the first digit (i) is 6 inches. 



The second metatarsal (ib., a) is 5 inches in length; vdth a proximal articular 

 surface 1 inch 6 lines in breadth, sinuous but almost flat : this surface presents 

 almost double the transverse extent in the antero-posterior direction. The inner 

 and anterior part of this surface is produced inward, or tibiad, apparently to 

 afford an abutment or attachment, at least in part, to the proximal end of the first 

 metatarsal. The outer or fibular side of the second metatarsal is almost straight, 

 the inner or tibial one concave, the expansion at both ends taking place chiefly in 

 that direction. The distal articular surface is convex from before backwards, with 

 a median groove producing a transverse concavity between the two convexities or 

 condyles, at the posterior half ; and these slightly project backward. The first 

 phalanx of the second toe is 1 inch 3 lines in length, 1 inch 7 lines across the 

 proximal, and 1 inch 6 lines across the distal end ; the diameter from before 

 backward at the middle of the shaft is 6 lines, the phalanx is consequently broad 

 and sub-depressed. The posterior or plantal surface at the proximal end is slightly 

 produced. The distal articular convexity extends a little way upon the middle of 

 the dorsal surface, and slightly swells out into two condyles at the opposite surface. 

 The second phalanx is much shorter in proportion to its breadth, which at the base 

 is 1 inch 6 lines ; the length being 1 inch 7 lines ; the tibial border is short and 

 concave ; the fibular one is straighter and one third longer. The ungual phalanx 

 {ii) differs chiefly from that of the first digit in its superior size, being 2 inches in 

 length and 1 inch 4 lines in its greatest breadth ; the fibular margin is convex, the 

 tibial one slightly concave. A side view of the bone, of the natural size, is given at 

 fig. 4, PI. 57. 



The length of the third metatarsal (ib.. Hi) is 5 inches 4 hues. It is more sym- 

 metrical in shape than the rest. The transverse breadth of the proximal end is 



