44 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 24, 
restrict the name Palwosaurus to the latter (or Megalosauroid) form 
of tooth, and to use T’hecodontosaurus for the former (or Scelidosau- 
roid) type, the varieties of which may be embraced under the common 
name of platyodon. 
The bones referred to and described by Riley and Stutchbury are 
vertebra, ribs of two kinds, a clavicle, two “ coracoids,” a humerus, a 
“radius,” two femora, an “ ischium,” a tibia, a fibula, metacarpal and 
metatarsal bones, and ungual phalanges. 
The “coracoid ” figured is, as I suspected, a fragmentary ilium. 
The “radius” I take tobe a tibia. The parts of the skeleton which 
diagnose the Dinosaurian nature of these reptiles, in addition to the 
teeth, are :—1, a caudal vertebra with the chevron bone; 2, anilium ; 
3, a tibia. 
The diagnostic mark in the first part of the skeleton mentioned 
lies in the complete union of the crura of the chevron bones at their 
proximal ends, in consequence of which coalescence the fork of the 
chevron bone is converted into a foramen (PI. III. figs. 5 & 6). 
This character appears to be universal among the Dinosauria. 
With respect to the ilium (Pl. III. fig. 7), it has every character 
of that bone in the Dinosauria. That part which enters into the 
acetabulum forms a semicircular arch, the piers of which are formed 
by the pree- and postacetabular processes (a, b), both of which are 
strong and trihedral. They are about equal in length; and each 
ends in a truncated face, which looks a little downwards and a little 
forwards in the anterior, downwards and a little backwards in the 
posterior process. The expanded supraacetabular part of the iium 
(c) is a vertically disposed plate, equal in height to the acetabular 
part. Anteriorly (d) it is produced in front of the acetabulum for a 
length equal to that of the neck by which it joins the acetabular part. 
Posteriorly (¢) it is prolonged into only a very short process, which 
does not project as far backwards as the postacetabular apophysis. 
In all these respects the Thecodontosaurian ilium exaggerates the 
peculiarities of that of AZegalosaurus. And the like is true of the 
form of the outer and inner surfaces, and of the superior contour, of 
the supraacetabular part. In the Triassic Dinosaurian the outer 
surface of this part of the bone is strongly concave from before back- 
wards above the acetabulum, the posterior iliac process being 
sharply bent outwards ; while it becomes flat above the anterior iliac 
process. Hence the superior contour has a sort of \-like curve. 
The supraacetabular part of the ium of MMegalosaurus has the 
same curvature, though less strongly pronounced. ‘The inferior 
surface of the anterior process of the supraacetabular part of the 
ilium of Megalosaurus presents a narrow groove, bounded on each 
side by ridges of bone. In the Thecodont, the place of the 
groove is taken by a broad surface which is only slightly concave 
from side to side. In Megalosaurus the posterior iliac process is a 
little longer than the postacetabular, and possesses a considerable 
height. In the Thecodont it is shorter, and much lower and more 
tapering posteriorly. 
