312 Mr. H. G. Seeley on Acanthopholis platypus, 



from above downward If inch. The distal end is ovately ob- 

 long, convex from above downward, whereas in the other bones 

 the condyles become more marked ; as in those bones, the me- 

 dian depression on this surface is only noticeable towards the 

 under'part ; and, as in the previous cases, the articular surface 

 is sligJitly oblique to the shaft laterally, inclining towards the 

 second bone. The surface measures 2^ inches wide by If inch 

 from above downward. 



The fourth bone is not well preserved, both articular ends 

 being rubbed. The bone is gradationally more slender than 

 that last described, and has proportionally smaller articular 

 ends ; it measures, as preserved, 5f inches in length. The 

 proximal articular end is triangular, measuring If inch along 

 the horizontal slightly concave superior surface, 2\ inches 

 along the flattened side towards bone 3, and 2| inches along 

 the flat side towards bone 5. The two sides meet below in a 

 rounded ridge proximally. The side towards bone 3 is gently 

 convex from above downward ; the side towards bone 5 is flat 

 from above downward proximally, convex from above down- 

 ward distally. All the sides are concave in length, the under- 

 side and that towards bone 5 most so, the superior surface 

 least so. In the middle the shaft measures less than an inch 

 from side to side, 1^ inch from above downward, as in pre- 

 viously described bones. Towards the distal end the bone 

 from above downward steadily contracts in depth up to the 

 enlargement made by the condyles of the articulation ; and, as 

 in the other bones, the distal end expands from side to side, 

 only more noticeably. The distal articular surface is like 

 those already described^ and oblong, with the sides convex 

 and the under sm'face slightly concave ; it measures more than 

 2 inches from side to side, and nearly 1^ inch from above 

 downward. 



The Jifth bone is badly preserved at its articular ends ; as 

 preserved, it is 5\ inches long ; it is in form much compressed 

 from side to side, and much expanded from above downward 

 at the proximal articulation. It is difficult to give the form of 

 this elongated area ; but its outline is flat on the inside of the 

 bone and convex on its exterior side ; it measures 3^ inches 

 from above downward, and 1^ inch from side to side, but does 

 not narrow inferiorly as it does superiorly, because the inner 

 angle is inflected so as to support the under part of bone 4. 

 The underside of the bone is very concave from back to front, 

 and well rounded from side to side ; but the side-to-side mea- 

 surement decreases towards the distal end. The inner side, 

 as remarked, is flat, and terminates above in a sharp ridge, 

 which extends down more than two-thirds the length of the 



