OP HYPSILOPHODON FOXTI. 
1053 
certain American Dinosauria* regarded as the homologue of the cuboid. In another 
foot between the astragalus and the base of IVth. metatarsal I found a small bone 
which may be the homologue of the external cuneiform. These identifications must 
be accepted with reservation; they must be confirmed or corrected by new and less 
disturbed materials. 
Metatarsus (Plate 77; Plate 79, fig. 4; Plate 81, figs. 2, 3).—The metatarsus of 
Hypsilophodon contains five bones, of which four are large and support functional 
toes, and one is rudimentary. The proximal ends of the four large metatarsals are 
in closest mutual apposition. Those of the two inner ones with the two distal tar- 
salia (if the identification of these latter be correct) form the distal half of the mid- 
tarsal joint where movement of the foot on the leg takes place. 
The distal ends of these metatarsalia are stout, their articular surface is pulley¬ 
shaped, the pits for the attachment of lateral ligaments are large and deep. Their 
long, slender, prismatic shafts have a slight forward and inward curve. Counted from 
the inner to the outer border of the foot, the Illrd. is the longest and largest meta¬ 
tarsal ; the IYth. is slightly longer than the Ilnd.; and this latter slightly exceeds the 
1st. The following table gives some dimensions of the metatarsals in a fully-grown 
Hypsilophodon :— 
I. II. 
III. 
IV. 
V. 
millims. 
millims. 
millims. 
millims. 
Length. 
t 93* 
105* 
87*5 
32- 
Breadth of proximal end. . . 
12* 
12*5 
8*5 
Breadth of distal end 
• ■ • • 
20* 
15* 
The Yth. metatarsal is a small tapering styliform bone, its distal end bluntly pointed 
does not support any phalanges. I found it first in 1876 in close relation to the IYth. 
metatarsal and os calcis , and I have since observed it in five other hind feet. 
Phalanges (Plate 79, fig. 4).—The four functional toes have respectively two, three, 
four and five phalanges, and therefore correspond to the 1st., Ilnd., Illrd., and IYth. 
toes in the foot of existing Lizards and Birds. The second, third, and fourth phalanges 
of the IYth. (outer toe) are shorter than the other phalanges, but this shortening is 
less than in the same phalanges in the foot of Iguanodon Mantelli and I. Prestwichii . 
The ungual phalanges are long, pointed, slightly curved, (Plate 79, fig. 4); their 
proportions to the metatarsals and other phalanges can be seen from the annexed 
table of measurements of the foot of an immature individual. 
* Marsh, 0. 0., “Principal Characters of American Jurassic Dinosaurs,” from American Journal of 
Arts and Sciences, vol. xvi., Nov., 1878, plate ix., fig. 3. Laosaurus. 
t Too mutilated for measurement. 
