Pelvic Girdles of Mureenosaurus plicatus. 433 
ischia, thus enclosing an obturator foramen on either side, 
cannot be determined, but it probably did so. 
Thetschia (7s) are hatchet-shaped bones, the upper thickened 
ends of which bear’ three articular surfaces—an anterior one 
Pelvic girdle of Murenosaurus from above. pu, pubis; zs, ischium ; 
a, ilium; f, femur. About !; nat. size. 
locking forwards for union with the pubes, a middle, looking 
outwards, forming the median portion of the acetabulum, and 
a posterior, looking upwards and backwards, for the ilium. 
The ventral expanded portion measures 21 centim. at the 
widest place; the median border is slightly curved and bears 
the impress of the cartilage which still separated the two 
bones; these also made an angle of about 120° with one 
another. ‘The symphysis of the pubes and ischia forms a 
curved line, convex dorsally. Hach obturator foramen (if 
closed) was oval, the shorter axis (antero-posterior) measuring 
10 centim., the longer 12. 
The tdium (il) is a slightly curved, stout, rod-like bone 18°5 
centim. long. Its lower end is stout and massive and bears 
two articular surfaces, one for union with the ischium, the 
other forming the hindermost portion of the acetabulum *. 
* The separation of the ilium from the pubis in Murenosaurus has 
been pointed out by Seeley (Proc. Roy. Soc. vol. li. (1892) p. 137); the 
same arrangement is described by Cragin in Trinacromerum (‘ American 
Geologist,’ vol. viii. (1891) p. 174), and is also shown in Conybeare’s 
restoration of the pelvic girdle of Plesiosawrus dolichodeirus (Trans. Geol. 
Soc. ser. 2, vol. i. (1824) pl. xlix. fig. 4). It also occurs in Pliosaurus, 
Peloneustes, and Cryptoclidus, and, indeed, is probably universal among the 
Plesiosauria. 
