28G PALAEONTOLOGY. 



triassic period, of an order of Reptilia which acquired its 

 full development and typical characteristics in the oolitic 

 period. 



Genus Scelidosaurus, Ow. — The earliest evidence of a 

 true Dinosaur is that on which the present genus was founded : 

 it consists of the largest proportion of the skeleton hitherto 

 obtained of any terrestrial herbivorous reptile. These inter- 

 esting remains were discovered by John Harrison, Esq. of 

 Charmouth, in the upper member of the lower lias on that 

 part of the Dorsetshire coast. The cranium shews the lacer- 

 tian T-shaped parietal, short and wide temporal fossa?, and 

 orbits bounded above by post-frontal, super-orbital, and pre- 

 frontal bones, the mid-frontals being excluded from the orbital 

 boundary. The malar and squamosal form a strong zygo- 

 matic arch below, and distinct from that formed by the post- 

 frontal and mastoid. Both upper and lower jaws are traversed 

 by a longitudinal ridge, from which the alveolar plates bend 

 inwards as they approach each other. The upper teeth pass 

 outside the under teeth when the mouth is closed. They are 

 sub-equal, and implanted in close-set sockets, so that the ex- 

 panded crowns slightly overlap each other. In Scelidosaurus 

 the crown diminishes in thickness to the apex, but gains in 

 breadth along its basal half, when the margins converge 

 straight to the pointed apex ; these margins are serrate, the 

 basal denticle being the largest. The femur is long,, with a 

 wide medullary cavity, and the third inner trochanter. Both 

 tibia and fibula articulate with the condyles at the knee- 

 joint. There are four digits to the hind foot, with broad, de- 

 pressed, obtuse claw-bones ; the number of bones, including 

 the metatarsal, in each toe, is respectively, 3, 4, 5, 6 ; the fifth 

 or outermost toe is reduced to a rudiment of the metatarsal. 



Genus Megalosatjrus, Bkld. — The true dinosaurian cha- 

 racters of this reptile have been established by the discovery 

 of the sacrum, which consists of five vertebrae, interlocked by 



