PROF. OWEN ON A CARNIVOROUS REPTILE. 97 



deltoid ridge (ib. b, b'), of similar basal extent to that in Felis, is more 

 produced and is much thinner, extending as a broad plate of bone 

 outward (radiad) and forward (thenad) ; it seems to be rather a 

 development in those directions of the entire shaft than to be a 

 superadded process of the shaft. The more rounded, thickened char- 

 acter which prevails through nearly the whole extent of the humerus 

 of the feline as of most mammals, is here confined to a constriction 

 barely an inch in extent between the subsidence of the deltoid al 

 or delto-pectoral crest and the beginning of the neuro-arterial bridge 

 (h) on the inner side, and of the supinator crest (e) on the outer side 

 of the lower two fifths of the bone. The perforation itself (1c) is more 

 highly placed, is further from the articular surface for the ulna, 

 than in Felis. The ulnar articulation or " trochlea " is less defined ; 

 the inner boundary ridge, so prominent m. Felis, is here undeveloped. 

 The convexity (fig. 6, g) for the radius, on the other hand, is relatively 

 larger, and its ball advances further upon the fore part of the shaft, 

 in the present fossil. In this, likewise, the anconal pit (fig. 7, d), so 

 deep and well-defined by outer and inner ridges in Felis, is a mere 

 wide and shallow triangular depression. 



The delto-pectoral crest (b, b') which seems to be a forward and 

 inward production of the outer border of the proximal part of the 

 humerus, is essentially a reptilian character of the bone. Its 

 ordinary proportions in existing Saurians are shown in Uromas- 

 tix sjpinipes (fig. 10, b, b') and in Monitor niloticus * ; in Croco- 

 diles the shortening of its base gives it more the character of a 

 distinct process; in Pterodactyles its development is chiefly in 

 transverse extent f; in Cynodraco the longitudinal extent prevails; 

 in Omosaurus the development in both directions of the delto- 

 pectoral crest is such as to have suggested the generic name of this 

 Dinosaur. But the perforation or canal (Ii, 7c, fig. 6) is not present 

 in any existing Reptile. There is, indeed, what may be loosely 

 termed a " supracondyloid foramen " in several Eeptilia. It is 

 noticed in the osteology of the genus Trionyx ; but its position in 

 the humerus is defined : — " The bone is perforated from before 

 backwards at the outer angle of the distal extremity "J. The 

 homologous supracondyloid foramen is shown in the humerus of the 

 Monitor nilotkus, in the under-cited monograph (Note * ), in pi. 

 xvii. fig. 6, at e', where it perforates a low supinator crest. Its 

 position in Uromastix sjoinijoes is shown at T and m in figs. 10 and 11 

 (Plate XI.). Dr. G anther notes the homologous foramen in the 

 humerus of Testudo elepJiantopus and its allies (Testado ephvppium 

 e.g.), and describes it as " the canal on the radial edge of the bone, 

 close to the elbow-joint, perforating the substance of the bone from 

 the front to the hinder side "§. 



* Monogr. on Omosaurus, pi. xvii. fig. 0, b, and fig. 0\ 



t Monogr. on Cretaceous Pterodactyles, 4to, 1800, pi. iii. fig. 9, b. 



\ ' Descriptive Catalogue of the Osteological Series contained in the Museum 

 of the Koyal College of Surgeons of England,' 4 to-, 1853, p. 184, Nos. 

 942, 943. 



§ Philos. Trans. 1875, p. 2GG, plate xlii. ; "b, radial canal for bloods ersels," 

 ib. p. 283. 



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