210 REPTILIA. 



Scelidosaurus (fig. 129). This early genus is known by one nearly com- 

 plete skeleton, besides many fragments. The head is remarkably small. 

 The end of the snout is unfortunately unknown, but the greater part of 

 the skull has been discovered, and the teeth are those of a herbivorous 

 animal, the crowns being more or less spatulate and serrated on the 

 edge. All the vertebrae are amphicoelous, and some of the centra are 

 proved to have an internal cavity. There are 6 or 7 cervical vertebrae, 

 16 dorsals, 1 lumbar, 4 sacrals, and probably about 40 caudals. The 

 scapula is long and narrow, the small coracoid disc-shaped and ex- 

 hibiting a perforation ; but the pectoral limb is imperfectly known. The 

 ilium is much extended, as usual. The femur, tibia and fibula are hollow, 

 and the latter are somewhat shorter than the first. The astragalus and 

 calcaneum are not fused with the tibia and fibula, and the imperfectly 

 determined small distal elements of the tarsus are ossified. The fifth 



FIG. 129. 



Scelidosaurus harrisoni; restoration of skeleton by 0. C. Marsh, one-thirty-sixth 

 nat. size. L. Jurassic (L. Lias) ; Dorsetshire. 



metatarsal is merely a small rudiment, but the others are well-developed 

 and the phalangeal formula is 2, 3, 4, 5, 0. Digit no. I, however, is 

 comparatively small and slender, so that the hind foot is functionally 

 tridactyle. The armour seems to have consisted of symmetrically dis- 

 posed longitudinal series of small tubercles and triangular or conical 

 scutes. The typical species is Scelidosaurus harrisoni, from the Lower 

 Lias of Lyme Regis, and seems to have attained a length of about four 

 metres. 



Stegosaums (figs. 130, 131). All the bones of this heavily armoured 

 Dinosaur are solid. The head is remarkably small, and the brain seems 

 to have been smaller in proportion to the size of the animal than in any 

 known land vertebrate. The teeth are very numerous, bluntly pointed, 

 and cylindrical or spatulate in form, arranged loosely in sockets in one 

 functional series on the maxilla and dentary ; their successors are lodged in 

 a large cavity in the bone. The vertebrae are slightly amphicoelous or with 

 flat ends, and most of the summits of the neural spines are expanded for the 



