KIMMERIDGIAN DINOSAURS. 573 



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

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

 of the acetabidum 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 vertebrae above noted the right femur and 

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

 PI. 72, 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., pi. 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 ?■, 

 answers to that in the ilium of the Igucmodon noted at p. 287.* But the proportions 

 of the antacetabular and postacetabular productions are reversed in the Kimmeridgian as 

 compared with the Wealden Dinosaiir.f 



The length of the antacetabidar part of the ilium in Scelidosaurus more resembles 

 that in Omosaurus, but it is narrower and extended more in the axis of the trunk, or is 

 less inclined outward. The corresponding part of the ilium in Cetiosaurus resembles in 

 breadth that of Omosaurus. In this the acetabular cavity (62) is thirteen inches in longi- 

 tudinal, nine inches in transverse extent. Its outer and hinder boi*der subsides at e, 

 and the cavity is continued upon the superacetabular surface of r, the break in the 

 boundary being somewhat analogous to the cleft in the more developed border of the 

 Mammalian acetabulum for the passage of vessels to the intra-acetabular synovial mass. 

 The lower or haemal part of the cavity is completed by the ischium (ib., 63), which 

 articulates syndesmotically with the surface (6, e)- There is no surface for the articulation 

 of a pubis with the ilium, the Omosaurus in this respect corresponding with the 

 Crocodilia. In the breadth also of the ilium as compared with the length that bone of 

 Omosaurus comes nearer to the Crocodilian than to the Lacertian type. 



And, again, in the extent to which the ilium is prolonged in front of the acetabulum 

 the Crocodiles^ depart less from the Dinosaurs than do the Lizards. In Lacerta 



* "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." 



t Compare ' Bmosauria,' PI. 10, fig. 1, 62' and 62", with PI. 72. 

 X Cuvier, ' Ossemens Fossiles,' 4to, 182-1, vol. v, pi. iv, fig. 15, a. 



