KIMMERIDGIAN DINOSAURS. 575 



the proportion, if any, contributed by the pubis to the acetabulum must have been very 

 small, for no trace of such appears. 



The pubis as it recedes from this joint gradually narrows to a breadth of 3 inches 



4 lines, then more rapidly expands to form the perforated pectineal plate (c). This plate 

 or process becomes, as in Lizards and Tortoises, thickened and tuberous at its free 

 prominent border, which describes a bold convexity before subsiding into the slender 

 continuation of the pubis (e,/). The margin of e continued thereto by the dotted line, 

 in figs. 4 and 5, is a fractured one ; and the angle of the border (e) to which the dotted 

 line is continued shows also fracture ; the extension of bone along that line is inferential. 

 Proximad of such fracture the anterior border of the pubis is entire and sharp, a continua- 

 tion of that which partly circumscribes the oblique pectineal hole or channel ('^). 



From the pectineal expansion the pubis contracts to a breadth of 2 inches, then 

 expands to its symphysial end {ff), which, when entire, must have had a breadth of from 



5 to 6 inches. The abraded surface (ib., fig. 7) gives a fuller ellipse than that of the 

 ischium (ib., fig. 3), but, as in that bone, indicates a symphysial junction with the opposite 

 pubis. The hind border of the pubis (/) is rounded and thicker than the fore border {e). 



The neural surface (ib., fig. 5) is feebly canaliculate lengthwise in part of its extent, and 

 this character is shown, though still more feebly, in the pubis of TJromastyx (fig. 9, 64). 

 But the accentuation of this surface in the broader half of the pubis of Omosaurus, as shown 

 in fig. 5, is due to crushing and fracture seemingly in relation to the original prominence 

 of the part of the pectineal process (c, fig. 5), which has been pressed to flatness with 

 slight concavity. 



I conclude from the length of both ischium and pubis that they diverged from each 

 other, viz., from their outer to their inner or symphysial ends, at an angle nearer that iu 

 Crocodihans than in Lacertians. There is no evidence or indication that these hseniapo- 

 physes were disposed otherwise than in the rest of the Reptilian class, meeting, each pair, 

 at the medial line, with a space between ischia and pubes, answering to a common and 

 uninterrupted obturatorial vacuity. This space, in Bicynodon, is obliterated by continuous 

 ossification. 



The length of the pubis in Omosaurus is 3 feet 6 inches, the extreme breadth is 

 9 inches ; the least breadth of the pre-pectineal part (*) is 3 inches 6 lines ; the extreme 

 thickness of this part is 1 inch 3 lines. 



Femur. — To the right of the pelvis lies the femur of the same side, with the 

 hinder surface exposed (PI. 73, 65). The head (a) of the bone is at a distance of 

 1 foot S inches from its socket («) and a little posterior to it. The distal end lies 

 exterior to and a few inches in advance of the right ilium. The terminal articular 

 surfaces of the shaft are, to some extent, worn away, but sufficient remains to show that 

 the chief convexity or head (,,) projected some inches within the inner longitudinal border 

 of the shaft, the proximal surface sloping slightly distad to the rough convex angle, 



10^ 



