C. W. Andrews — On the Pelvis of Cryptoclidus. 147 



thins suddenly, thickening again towards the posterior angle. The 

 two ischia were separated in front by cartilage which, as already 

 mentioned, was probably continuous with that between the pubes ; 

 posteriorly there was, no doubt, a small " hypogastroid " cartilage. 



The articular end of the ischium is extremely massive, measuring 

 about 7 cm. in thickness at the acetabulum. As in Mnranosaurus, 

 it bears three articular surfaces : of these, the anterior, for the pubis, 

 is nearly semicircular ; the median, forming the middle part of the 

 acetabulum, is roughly rectangular, and measures 6 cm. from before 

 backwards; the posterior, for the ilium, is about 5 cm. long, and looks 

 backwards and only slightly upwards, the ilia being directed much 

 more backwards than in Murcenosaurus. 



The dimensions of the ischium are — 



cm. 



"Width from acetabulum to middle of symphysial surface 22 



Length between the anterior and posterior inner angles 21 



Width of neck at narrowest point 6-8 



Circumference ,, ,, ,, 16 



Ilium. — The ilium is a very stout, slightly curved rod of bone. 

 Its lower end is greatly thickened, and is truncated by an oblique 

 oval surface, the long diameter of which is 7-5 cm. in length ; the 

 short, 4-5 cm. The inner two-thirds of this nearly flat surface 

 articulate with the iliac surface of the ischium, while the outer 

 third forms the posterior wall of the acetabulum. The outer angle 

 of the acetabular region is occupied by a small surface for cartilage, 

 which probably capped this portion of the bone and was continuous 

 with that lining the acetabulum. The middle of the ilium is con- 

 tracted and is slightly oval in section. The upper portion is 

 compressed and somewhat like the blade of an oar. The anterior 

 border of this expanded region is thin and sharp, the posterior thick 

 and rounded ; its upper edge is curved and bears a surface for 

 cartilage. The inner face of the upper portion of the ilium is flat 

 and shows scarcely any trace of its union with the sacral ribs, to 

 which it was probably only loosely attached by ligaments. The 

 distance between the upper ends of the ilia is about 23 cm. The 

 length of the ilium is 20 cm., the width of its upper end 6 cm., and 

 the circumference of the shaft at the narrowest point about 11cm. 

 The lower end of the left ilium has been restored in plaster. 



Looking at the pelvis as a whole, it will be seen that it presents 

 some peculiar characters. The pubes and ischia of the opposite 

 sides do not make a distinct angle with one another; on the contrary, 

 their middle portions are almost in the same plane, and the visceral 

 surface of the pelvis is only gently concave from side to side. This, 

 combined with its great width, gives the whole pelvis a peculiar 

 appearance of extreme shallowness and expansion. From before 

 backwards the visceral surface is strongly convex, its highest point 

 between the acetabula being only about 85 cm. below a straight line 

 joining the middle points of the upper borders of those cavities. 

 In front of and behind this point it slopes away towards the 

 anterior and posterior borders of the pelvis. 



