Among reptiles, the bone may be compared with lizards and crocodiles. In crocodiles the proximal and distal ends are nearly in the same plane, the distal end has two condyles, the head is convex from side to side, and the radial crest is moderately developed and never extends so far outward or so far proximally as in Pterodactyle. In the Chameleon the bone is more twisted than in Crocodile, and as in Pterodactyle the distal end is compressed on the radial side to a sharp margin. In Iguana, Scink, and Monitor both proximal and distal ends are much expanded, and the radial process makes no approximation to that of a Pterodactyle. The bird humerus does not approximate more closely in form to that of the Pterodactyle than does the Chameleon humerus, though it has the cardinal distinction of pneumatic foramina, and these sometimes corresponding in position in the two groups. The bird humerus is commonly longer, though in the parrots the proportions and straightness are not unlike Pterodactyle. In some respects a nearer resemblance is seen in the raptorial bird _Gypogeranus serpentarius_, in which the radial process is rather more developed than in the Crocodile, and extends further proximally though still much smaller than in Pterodactyle; here too the superior surface is concave from side to side, and the distal articulation is not unlike that of some Pterodactyles. But no Pterodactyle has the head of the humerus convex from the radial to the ulnar sides, and the bird is distinctive in having the ulnar crest developed on the inferior side of the head: a faint approximation to a similar development is seen in Crocodile, but there is no trace of such a process in Pterodactyle. The distal end is more Bird-like than Lacertian in form, but is twisted to a greater angle with the proximal end than in birds. Altogether the bone is distinctive. The points in which it is unlike birds and reptiles are those in which Birds and Lizards resemble each other; it would not be easy to say that in form it resembles one group more than the other. But it is linked with birds by the pneumatic foramina. RADIUS AND ULNA. Case. Comp. Tablet. Specimen. =J= _a_ 9 5- 6 10 1-10 11 1- 7 12 1- 4 13 5- 6