No. 2.] THE RELATIONS OF PROTOCERAS. 353 



which the proximal part of mt. II lies and on the fibular side 

 is a narrow, concave facet into which a projection from mt. IV 

 is received. The shaft is stout, slightly contracted in the 

 middle ; proximally it is laterally compressed and has its 

 greatest diameter in the dorso-plantar direction, while distally 

 it is broadened and flattened and its longest diameter is trans- 

 verse. This is in accordance with the shape of the metatarsal 

 in the Pecora, in which the hind cannon-bone is laterally com- 

 pressed in its proximal portion, while the fore cannon-bone is 

 compressed from before backward, but in Protoceras the differ- 

 ence is not so distinctly marked. The contact surfaces of the 

 median metatarsals are flattened, allowing the two to be very 

 closely approximated ; the plantar side is also flattened, but 

 the dorsal and apposite surfaces form one continuous curve. 

 The distal trochlea is strongly convex and is demarcated from 

 the shaft by a shallow pit ; the carina, as in the metacarpal, is 

 confined to the plantar side, but is a little more strongly devel- 

 oped than in the manus. 



The fourth metatarsal is the counterpart of the third and 

 exceeds it but very slightly in length ; it projects somewhat 

 below the distal end of mt. Ill, but this is nearly compensated 

 by the fact that the head of the latter rises a little above that 

 of mt. IV. The plantar hook is very prominent and bears a 

 facet for the one upon the hook of the cuboid. The fibular 

 side is excavated for the head of mt. V, and there is a minute 

 articular surface for that bone ; the fossa, however, is not 

 nearly so deep and wide as that on mt. Ill, which receives 

 mt. II. The articulation with mt. Ill is by means of a small 

 but prominent process on the dorsal margin of the proximal 

 end, which fits into a corresponding depression on mt. Ill, 

 and also by flat surfaces on the approximate sides of the plan- 

 tar hooks. According to Osborn and Wortman, some speci- 

 mens show a tendency to the ankylosis of the median metatar- 

 sals; but none of those in the Princeton collection, even of 

 aged individuals, exhibit any traces of such a process, and it 

 would appear to be very exceptional. 



The fifth metatarsal is a short, tapering splint ; it articulates 

 with a small facet on the fibular side of the cuboid and with 



