94 Mr. Owen on the Glyptodon clavipes. 



The third or middle metatarsal bone is the largest of the three ; it diminishes 

 in breadth, but greatly increases in antero-posterior thickness from the upper to 

 the lower surface : the posterior articular surface is very slightly concave, and is 

 nearly exclusively applied to the external cuneiform bone above-described : a small 

 portion is deflected forwards from its upper and inner side to be applied to the 

 oblique facet in the depression on the outer side of the second metatarsal : there is 

 a similar depression and articular facet on the upper and outer side of the present 

 metatarsal, in Avhich a corresponding process of the fourth metatarsal is wedged. 

 By this structure the three principal metatarsals are interlocked together, and any 

 force or concussion from the toes would thus be transferred not only directly back- 

 wards to the tarsal bones, but obhquely from one metatarsal to another, whereby 

 peculiar strength and security is given to the bony compages of the foot. The 

 anterior surface of the middle metatarsal is slightly convex, two inches long by one 

 and three quarters wide, which gives an idea of the bulk of the first phalanx of the 

 middle toe : the under part of the present metatarsal bone presents two broad 

 concave grooves for large sesamoid bones. 



The fourth metatarsal is smaller than the second ; its outer rough surface is 

 convex, its inner one nearly straight, but with a small concave facet bounded by a 

 raised ridge, and adapted to the convex articular surface in the depression on the 

 opposed surface of the third metatarsal : the oblong posterior articular surface 

 adapted to the os cuboides is slightly concave, with the transverse diameter equal 

 to half the vertical one : the anterior surface for the fourth toe is triangular and 

 nearly flat ; there are two sesamoid grooves on the under part of this metatarsal 

 bone. There are no remains of the small external or fifth toe, but its existence is 

 indicated by a very small flat articular facet on the outer side of the fourth meta- 

 tarsal bone, and by the extent of surface on the cuboid which it leaves uncovered. 

 There is no evidence of the relative size of the first or innermost toe. 



The three phalanges of the second, and the middle and distal phalanges of the 

 third and fourth toes, are fortunately preserved. The proximal phalanx of the 

 second toe* is a vertically oblong, compressed, plate of bone, thicker above than 

 below in the antero-posterior direction ; a protuberance rises from the middle and 

 posterior part of the upper surface ; the lower margin presents a deep and narrow 

 notch. The posterior surface is shghtly concave, the anterior one flat, with a 

 rough spot in the centre. The second phalanx of the same toef is still more com- 

 pressed ; its greatest length or antero-posterior extent, which is at the upper part, 

 measures only six lines, whilst its vertical diameter is twenty lines, and its trans- 

 verse diameter seventeen lines ; its lower margin is notched like the preceding 

 phalanx, and at the middle of the posterior articular surface there is a central 



* PI. XII. fig. 1, 1 ; fig. 2. t Ibid, fig. 1, 2 ; fig. 3. 



