﻿62 



FOSSIL REPTILIA OF THE 



is broad. The thenal surface is made concave lengthwise by the thenal production of the 

 terminal lobes of the distal end (PI. XV, fig. 5). There is no appearance of these being 

 articular. I regard them as the free termination of a last or ungual phalanx, and to show 

 a modification of that end like the terminal phalanx of the second toe in Iguanodon 

 (Monogr. cit. Pal. vol. for 1871, PI. Ill, a, 3). 



Not any of the fragments of phalanges suggested a structure for supporting a terminal 

 claw, such as exists in Megalosaurus. The fore-foot of Omosaurus, as represented by the 

 bones above described, was a short, broad, massive member, relating chiefly to progressive 

 motion, and suggests the huge species, if not, like Iguanodon, phytophagous, to have been 

 a mixed feeder. 



§ 11. Ilium. — The mass of matrix with the portion of the skeleton of Omosaurus figured 

 in PI. XIX, reduced to one ninth of the natural size, includes, with the sacrum, both the 

 iliac] bones and a large portion of the right ischium. The left ischium and both pubic 

 bones, one of which was almost entire (PI. XX, figs. 4 and 5), were wrought out of the block 

 in the course of exposing the rest of the pelvis upon which they were lying dislocated. 



The length of the ilium is 3 feet 5 inches ; that of the antacetabular portion is 1 foot 

 9 inches ; that of the postacetabular portion is 9 inches, but the end of this is broken 

 off on k both sides ; the breadth of the superacetabular portion is 7 inches ; the length 

 of the acetabulum is 1 foot 1 inch ; the breadth of ditto is 9 inches ; the extent of the 

 unwalled part of the cavity is 7 inches. 



Besides the pelvis and the detached vertebras above noted the right femur and 

 probably the shaft of the fibula were left in the mass in the relative positions exposed in 

 PI. XIX, in which the pelvis is seen from the haemal (ventral or lower) aspect. 



The ilium (ib., 62—62") is an oblong, broad, and thick bone, anchylosed by a neu- 

 romedial tract, two feet in length, to the expanded ends of the five sacral ribs 

 (ib., p i. I-V). 



The haemal surface is divided into an acetabular tract (62) } an antacetabular production 

 (62') of greater antero-posterior extent, and a shorter postacetabular production (62")- 



The lateral or external surface, or superacetabular tract, extends neurad and 

 outward to terminate in a thick rugged convex border (?•), which is continued forward, 

 subsiding as a ridge upon the outer or neural surface of the antacetabular prolongation, 

 (62') ; the ridge is lost about nine inches from the fore-end of the antacetabular plate, 

 and gives a triedral form to this part of the ischium. The ridge, continued from r } 

 answers to that in the sacrum of the Iguanodon noted in Pal. vol. for 1S54, ' Wealden 

 Reptilia/ Part II, p. 13. 1 But the proportions of the antacetabular and postacetabular 

 productions are reversed in the Kimmeridgian as compared with the Wealden Dinosaur. 2 



1 "The outer surface is divided into two facets by a strong longitudinal ridge, for the attachment of 

 some of the powerful muscles of the hind limb." — P. 13. 



2 Compare PI. Ill (Monogr. cit.), 62' and 62", with PL XIX of the present Monograph. 



