54 
thickest and flattened in the way commonly seen in Ornithischian 
reptiles. Anteriorly, there is a concave channel between the 
two trochlear ridges which are hut slightly elevated in front of 
the distal articulation. The inner ridge is narrower and more 
elevated than the outer ridge, which has a wider, rounded 
aspect. 
On the external side of the distal articulation there is the 
usual concave longitudinal channel towards the posterior 
margin, which, being defined by a transverse widening of the 
bone, makes this external surface convex from above down¬ 
ward, and contributes to compress the external condyle, which 
becomes the distal termination of a convex ridge extending 
down the shaft at about one inch from its external border. 
The inner condyle was moderately developed, though larger, 
and it was rounded. Its base is two inches wide. The whole 
of the under side of the distal end of the shaft is concave from 
side to side. 
The contour of the articulation seen from the distal extremity 
is transversely oblong. The surface is rounded downward and 
backward: with an almost inappreciable depression between 
the inner and outer portions. The inner condyle extends a 
little further distally than the outer condyle ; and this leads to 
the inference that the femora diverged outward in a way that 
would be consistent with a prone condition of the animal’s 
body. 
Such are the characters of the femur which has remained for 
55 years the only evidence of this animal. Every detail of 
structure proves it to conform so closely to the type which is 
known as Omosaurus that it may be regarded as indicating a 
new species of that genus. Its generic identification is based 
upon the straight compressed shaft in which there is no 
appreciable twist; on the proximal trochanteric ridge, the 
absence of a trochanter on the middle of the inner side of the 
shaft, and the forms, proportions and characters of the proximal 
and distal ends. Omosaurus is known from the Oxford and 
Kimeridge Clays. The former evidenced by the 0. clurobrivnisis 
(Hulke) based upon the specimen in the British Museum 
obtained from near Peterborough by Mr. A. N. Leeds, and 
the latter by 0. annatus (Owen) from Swindon which is also in 
