OSTEOLOGY OF CARNIVOROUS DINOSAURS. 113 



found in Antrodemus. 1 and in the mounted skeleton this digit has heen restored as 

 shown in plate 30. The metatarsals are so fully illustrated in all aspects in plates 

 24 and 25 that a detailed description appears unnecessary. 



Measurements of metatarsals of Ceratosaurus nasicornis Marsh. Cat. No. 4735, U.S.N. M. 



mm. 



Greatest length of metatarsal II '230 



Greatest length of metatarsal III 254 



Greatest length of metatarsal IV 220 



Greatest width of coalesced metatarsal, proximal ends 120 



Greatest width of coalesced metatarsal, distal ends 146 



The metatarsals of Ceratosaurus are nearly a third shorter than the correspond- 

 ing elements of a fully adult Antrodemus specimen, though the relative lengths of 

 of the metatarsals to one another in the respective feet are very similar. 



The most pronounced differences observed are found in comparing the proximal 

 ends to the metatarsals of these two genera. This end of metatarsal III in Antro- 

 demus is elongated anteroposterior^, wide in front, and rapidly narrowing poste- 

 riorly, whereas in Ceratosaurus'it is wider behind than in front. Viewed from above 

 metatarsal III of ' Ceratosaurus is subrectangular in outline as compared with the 

 elongated triangular end of the Antrodemus metatarsal. Viewed from the poste- 

 rior side metatarsal III of the Ceratosaurus foot forms the greater part of this view, 

 whereas in Antrodemus the fourth has the greatest expanse. These and other 

 differences can be clearly seen by comparing figure 51 with figure 4, plate 24. 



DERMAL ARMOR. 



Plates 22 and 29-30. 



Several dermal ossifications were found with the type specimen of Ceratosaurus 

 nasicornis, and some of these were so retained in the matrix as to indicate their 

 exact position in relation to the internal skeleton of the living animal. Reference 

 is made here to the row of elongate, irregularly shaped, bony ossicles present above 

 the spinous processes of caudals (fig. 1, pi. 22) 4 to 10 inclusive, and above cervicals 

 4 and 5 (0. pis. 29 and 30). The position of these ossicles would appear to indicate 

 a continuous row of dermal ossifications, extending along the median line of the 

 back from the base of the skull well down on the tail, if not the greater part of its 

 length. In the life restoration of this animal by Knight and Gleeson (pi. 28, upper 

 figure) such an external ornamentation has been indicated, though the size of the 

 plates is somewhat exaggerated. 



The ossifications above the tail are from 25 to 38 nim. above the tops of 

 the spinous processes of the vertebrae, evidently indicating the thickness of skin and 

 muscles between them and the tops of the spines. Those on the neck are much 

 closer to the vertebrae, and in one instance appears to rest on the spine (figs. 1, 2, 

 and 3, pi. 20). 



That there were other dermal ossifications is shown by the presence of a small 

 skin plate found with the bones of this skeleton. It had been freed from the matrix 

 when it came into my hands, so there is no evidence as to its probable position in 



i Osborn, H. F. Bull. Amer. Mus. Nat. Hist., vol. 12, 1899, p. 163, fig. 3. 



