separated at the base, making the articulation wider than the shaft. In No. 31 the three inches of the shaft which remain show both pairs of its sides sub-parallel; the widest measures nearly an inch; the base of the articulation is less than a quarter of an inch wider. Limited to the base, between the two outer ridges of the pulley, is a short median ridge slightly developed; so as to flatten the middle of the concavity between the ridges, and divide it into two grooves. The degree to which the middle ridge is developed varies in different species. In No. 30, the smallest pterodactyle, remarkable for a long wing-metacarpal bone, it is not to be detected. The exterior sides of the trochlear articulation are broad, flattened, and a little concave. There is some variation in the way in which the shaft is set on the trochlear end. It being often in the middle, but not unfrequently inclined more to one side than to the other. The metacarpus finds no close parallel among living animals. The thread-like metacarpal bones suggest the condition of the hind-foot in the Kangaroo. The predominant metacarpal suggests the ruminants. But the nearest approximation is found among birds where the bone for the middle finger is large and the bone for the third finger is slender. This may be observed (among other examples) in the Penguin and the Swan. But here the parallel ends. The proximal end in Birds, we have already seen to be hidden by the anchylosed distal row of the carpus, and the distal end though often convex from side to side never presents the trochlear joint of the Pterodactyle. Consequently so far as regards the form of the articular ends the resemblance is closer with Reptiles and clawed Mammals than with Birds. In Birds the small metacarpal is usually of similar length with the large one as is the case with Pterodactyles. FIRST PHALANGE. Pl. 7. Case. Comp. Tablet. Specimen. =J= _b_ 6 1-10 No perfect specimen of the first phalange has been found in the Cambridge Greensand. Ten bones are mounted to illustrate it, all of them less perfect than others in the series of associated bones. No. 1 shows the heel of the proximal end; Nos. 9 and 10 are portions of the proximal articulation from which the epiphysis which forms the articular heel-part seen in No. 1 has come away. Nos. 2 to 8 are the distal articular ends of first phalanges. It is improbable that any of them belong to the second phalange, since they agree in form, and show muscular attachments which correspond.