LIASSIC FORMATIONS. 
39 
joining the corresponding parts of the pubis ; the outer acetabular angle is produced, 
and terminally expanded and thickened to form the articular surfaces for the ilium 
and femur. 
The pubis (ib., 64), as in other Plesiosauri, is broader and larger than the ischium, 
with the medial or symphysial margin straight, measuring six and a half inches in 
extent; the anterior and external free margin is convex; the posterior margin is more 
deeply excavated than the opposite one of the ischium, forming a greater part of the 
circumference of the obturator foramen ; the angle between the posterior and outer 
borders is thickened, to contribute the anterior part of the acetabulum. This rough 
and ill-defined articular surface for the femur is thus formed, as usual, by the three 
constituents of the pelvis. 
The femora (ib., 65) here, as in some other Plesiosauri, have the head resting against 
the ischio-pubic part of the acetabulum, the ilia being placed about an inch further 
back. The femur, 10 inches in length, is 1 inch 9 lines across the narrowest part of 
the shaft, and expands to a breadth of 4 inches 9 lines distally ; the outer (here the 
upper) part of the head is produced, and behind it is a longitudinal depression. The 
surface, for two inches or more from the distal end, is rugose, with longitudinal ridges 
breaking up into tubercles ; both anterior and posterior borders are concave ; the latter 
is the shorter border. The distal border is more regularly convex, and in a greater 
degree than in the humerus. 
There is an interval between the proximal ends of the tibia and fibula, and a wider 
one between their distal ends, the interosseous space being considerable, as in the 
forearm. Here, also, the tibia (ib., 66), like its homotype (ib., 54), has a more distal 
extension. Its length is 3 inches 11 lines, its proximal breadth ^2 inches 8 lines. The 
anterior proximal angle is somewhat produced ; the anterior orbital border is slightly 
concave ; the posterior one is more so. The fibula (ib., 67), like the ulna, departs from 
the ordinary reniform figure by the production of its fibular proximal angle (67') ; this 
is not separated from the rest of the bone in the left leg, but it is so by what appears 
to be a crack in the right leg, and yet so as to indicate that sueh crack is in the place 
of an original epiphysial junction. The length of the fibula, including this process, is 
4 inches 4 lines ; the length of the concave tibial border of the fibula in a straight line 
is 2 inches 3 lines. As great a proportion of the exposed surface of the leg bones is 
rugose as is that in the bones of the forearm. Between the tibia and the tarsal bone 
supporting the first metatarsal there is a vacant space in both limbs, which, in the 
right limb, is partially occupied by a tubercle of bone. This we may regard as the 
beginning of ossification of a fibro-cartilaginous homologue of a naviculare (Tab. XIV, 
fig. 3, s). The homotype of the lunare (a) completes, by a free concave part of its 
border, the distal end of the inter-osseous space. This tarsal («), which we 
may call “ astragalus,” articulates with the tibia (66) ; but to a greater extent and 
by a more definite straight border, with the fibula (ib., 67) ; posteriorly with the 
