o 4 o HEPTILIA class m 



bo ten times the capacity of brain cavity (Fig. 347). Anterior caudal vertebrae 



Stegosaurus stenops, Marsh. 



Fig. 346. 



Upper Jura ; Colorado. Superior and lateral aspects of skull, 

 i/ 6 (after. Marsh). 



a 



the largest in the column, and with strong chevron bones. Fore-limb short 

 A and stout, ulna with large olecranon pro- 



cess. Manus short, apparently penta- 

 dactyle. Femur large and straight, 

 without inner trochanter ; tibia and 

 fibula much shorter. Astragalus and 

 calcaneum fused with opposing bones of 

 the cms ; pes triclactyle, digit No. I 

 rudimentary, and No. V wanting. 

 Dermal armour consisting of two rows 

 of flattened bony plates extending from 

 the back of the head well down the tail, 

 the largest plates situated immediately 

 over the pelvis. Four spines on the 

 tail, and throat protected by a shield of 

 irregular ossicles. Known by complete 

 skeletons from the Upper Jura of 

 Wyoming and Colorado. S. unguhtus, 

 Marsh, over 9 m. long. 



Diracodon, Marsh. Is 

 founded on the young of this species. 



ScelidosauruSj Owen. Skull only 

 about 0'25 m. long. Teeth with tri- 

 angular or spatulate crowns, coarsely 

 serrated on the margins. All the centra 

 amphicoelous, some with an internal 

 cavity, and the neural canal not expanded. There are six or seven cervicals, 

 sixteen dorsals, one lumbar, four sacrals, and about forty caudals. Femur, 



-m, 



probably 



Fig. 347. 



rus ungulatus, .Marsh. Upper Jura; 



irado. A, Gutta-percha east of neural canal in 



sac-ruin, dorsal aspect, ] /4- B, Same of brain cavity, 



a, Anterior end; c, Cerebral hemispheres; cb, 



Cerebellum ; /, Vacuities between transverse pro- 



s of sacrum ; m, .Medulla oblongata; ol, Olfac- 



bory lobe; op, optic lube ; y<, Posterior end. 



