ON SOME MES0Z01C FOSSILS. 
high probability that time was when the brain within the skull 
actuated these bones without it. The straight and rather slender 
tibia has the cylindricitv of its shaft only marred by a very moderate 
flattening over the middle of its diameter and expands gently from 
about its mid length towards each terminal limit. Its articulating 
borders have the customary incrassation, convexity in both directions, 
and want of surfaces differentiated for articular requirements. 
Fibula. — The fibular moiety of the segment is of still greater 
interest. It is considerably longer than the tibia, slightly broader 
at its proximal, nearly as broad at its distal end, and rather thicker 
in the shaft, which has so strong a curvature that the interosseous 
space equals its own remarkable diameter. The superior size 
of this bone is not without significance ; its muscular investment 
must have been capable of communicating an unusually powerful 
outward sweep to a natatory foot. 
The proportions, inter se, of these bones in their several 
dimensions may possibly tend to influence opinion respecting the 
zoological standing of Notochelone, and are therefore worthy of 
consideration. They may be most succinctly expressed in the 
tabular form subjoined : — 
Femur. 
Length (from summit of great trochanter) 
Minimum diameter 
Trochanterian width 
Distal width 
Length 
Min. diam. 
Proximal width 
Distal width 
Length 
Min. diam. 
Proximal width 
Distal width 
Tibia. 
Fibula. 
NOTOCHELONE. 
Measurements 
Ratio to 
in mm. 
Length. 
70 
8* 
i-8 
23^ 
13 
22 
1-3 
72 
i : 8 
18 
1-4 
12 
1-6 
81| 
10 
1-8 
18 
1-4 
12i 
165 
On the removal of matrix overlying the area immediately behind 
the distal ends of the long bones there appeared an osseous mass, 
denuded of its outer structure before burial, defined as to its hori- 
zontal limits by the exposed edges of that structure and without 
