LIASSIC DINOSAURS. 115 



To the major part of the distal end of the tibia, at least to two thirds of its 

 inner or tibial side, is articulated the tarsal bone («), including the coalesced 

 homologues of the astragalus, naviculare, with the ento- and meso-cuneiform bones, 

 of the mammalian tarsus. This bone (PI. 57, fig. I, a) presents an anterior surface 

 of an elongated, irregular, triangular form, with the apex tibiad or toward the 

 inner side of the tarsus. It becomes narrower as it proceeds backward beneath 

 the tibia (ib., fig. 3, a), its articular surface with which is concave from before 

 backward, favom^ing flexion and extension, or motion of the foot to and fro. Its 

 distal surface is convex in the same direction, and is sinuous transversely. 



The calcaneum (ib., figs. 1 and 3, Z) articulates with the distal end of the fibula 

 (fig. 1, 67) and with the outer third of the same surface of the tibia (fig. B,l). 



The next most intelligible tarsal bone is that (figs. 1 and 3, i) which articulates 

 with the calcaneum (f) and with the two outer metatarsals Uv and v). Its largest 

 surface is tm-ned forward or upward ; its posterior surface is a smaller convex 

 protuberance ; this bone answers to the cubo'ides. 



At the back part of the tarsus there projects the base of a wedge-shaped bone, 

 (fig. 3, e) seemingly partially dislocated backward, which mainly supports the 

 middle metatarsal (m), and extends partly over the fourth (fig. 3, iv). The apex 

 of this bone appears on the front side of the tarsus (fig. 1, e) in the interspace 

 between the astragalus {„), cubo'ides (j), the third and the fourth metatarsals. 

 I regard this bone, therefore, as answering to the ecto-cuneiform ; I cannot discern 

 any trace of other cuneiform bones, the fibro-cartilage by which the interspace 

 between the bone («), and the first and second metatarsals, was most probably 

 occupied held partly the place of the meso- and ento-cuneiform bones. From this 

 it appeal's that the tarsus of Scelidosaurus includes but four bones, as in the Crocodile 

 (PI. 58, fig. 4.) In the Lizard (Varanus), fig. 3, an ossification in the fibro-car- 

 tilage at the base of the second metatarsal establishes the " meso-cuneiforme," and 

 leaves the " ento-cuneiforme " to combine with the naviculare and astragalus in the 

 bone (a). 



The metatarsus of Scelidosaurus consists of five bones. Of these, the fifth 

 (PL 66, figs. 1 and 3, v) is abortive, and adherent to a rough ridge on the outer 

 part of the base of the fourth metatarsal, with its proximal half extending over the 

 interspace between tliat bone and the cuboid to articulate with the latter. It was 

 not, however, flattened and expanded, as in the Crocodile (PL 58, fig. 4, «), but 

 was slender and styliform, if we may judge by the proximal end which fortunately 

 remains attached in the left hind foot of Scelidosaurus (PL 57, fig 1, »). It most 

 probably did not support a toe, or make any distinct appearance in the entire foot. 

 The other four metatarsals support each a fully-developed toe, with the progressive 

 increase in the number of phalanges characteristic of sam-ian EejAiUa ; the first 

 having 2, the second 3, the third 4, and the fourth 5 phalanges. 



