THE CAMBRIDGE GREENSAND. 611 
shallow grooves, which may indicate that it possessed a terminal 
articular cartilage, though developed to a less extent than in the 
Ceteosaurians of the Lower Secondary rocks. Towards the ulnar 
side the articular surface becomes narrow and prolonged, like the 
stalk of a fig (fig. 4,¢); but this portion is inclined at an angle of 
about 45°. It is nearly flat in its long measurement, which is more 
than an inch, and slightly rounded in its narrow measurement, which 
appears to have been less than three quarters of an inch. It gives 
an extreme length of articular surface to the head of about 1,5 inch. 
Externally the ulnar margin is well rounded from side to side, 
about =$ inch thick, and by its compression forms on the dorsal 
surface a concave longitudinal channel, which descends some little 
distance on that aspect of the bone. Below the articular head of 
the bone the shaft is convex from side to side, but becomes rapidly 
compressed, so that 2 inches below the articular surface its thickness 
is scarcely Linch. The fragment is unfortunately only about 2 
inches long; it shows indications of the lateral margins rapidly 
converging, is marked on the dense external layer with longitudinal 
striz, and shows at the fractured end fine cancellous tissue, but no 
trace of a medullary cavity. 
Distal end.—The distal end (fig. 5) apparently formed an angle with 
the proximal end in the usual way, so far as can be judged by compa- 
rison of the proximal and distal fractured surfaces of the humerus. 
The distal fragment is 44 inches long, and at its proximal end has a 
subtriangular section, measuring nearly 13 inch in the greatest long 
diameter, from the ulnar to the radial sides, and about 1 inch in the 
greatest short diameter, which is towards the ulnar side from back 
to front. It will thus be seen that the bone is compressed towards 
the lower radial margin, and the strong crest which is there indi- 
cated is the distal termination of the radial crest. The long axis 
of this section is at an angle of about 45° to the axis of the 
distal articulation. The ventral side is here flattened, but has a 
slight indication of a longitudinal concavity. The dorsal aspect is 
divided into two areas by a rounded angular bend, that of the ulnar 
side is the shorter and less convex. The shaft continues to decrease 
in thickness towards the distal end, where it measures, just above 
and between the condyles, ;9, inch, and it more rapidly increases in 
width, though, from the radial condyle being broken away, it is im- 
possible to state accurately what the width was, though it could not 
haye been less than 3 inches. 
Metacarpal bone.—This small well-preserved specimen I am in- 
clined to regard as the fifth or outer metacarpal of the left fore 
limb. It is 1,4; inch long, and has the proximal articulation subtrian- 
gular, 59; inch wide and 58; inch deep, with the apex of the triangle 
below. The articular surface is nearly flat, but slightly oblique, as 
shown in the figure (Pl. XXXYV. fig. 9). 
The bone is compressed from above downward, ;°, inch wide in 
the middle of the shaft and 54, inch deep. It terminates distally 
in an oblong surface, which is conyex from above downward and 
from within outward, and has the upper outer corner rounded away. 
The surface is fully 35) inch long and ;%) inch deep. 
