64 
1CHTHY0SA URIA FROM THE 
Case. Shelf. No. 
X f 1—14 smaller than the proximal end, rather 
larger than the adjacent part of the shaft; 
it is oblique to the head. These bones 
demonstrate at least three well defined 
species; f. 10, 11, 13 illustrate them. 
X f 15—28 Femur. The femora are all as large as the 
humeri; and the largest femora, f. 15, 16, 
are much larger and more massive than 
any known specimen of humerus of Icthy- 
osaurus from the Cambridge Greensand. 
Nos. f. 15—22 are left femur. Nos./*. 23 
—28 are right femur. They indicate at 
least five well defined species; f. 15, 17, 
18, 21, 28 illustrate them. 
The under side is usually flattened, the 
upper side convex, with a more or less 
defined longitudinal ridge, which slightly 
curves so as to indicate that the greater 
part of the head lies behind the plane at 
right angles to the distal articulation. 
The proximal end is circular, sub-rhomboid, 
or crescentic, it is convex, and sends off 
on each side a trochanteroid process which 
makes the head massive; they extend 
down the short shaft towards the under 
surface, but do not reach the distal end. 
The distal end is usually small and com¬ 
pressed, of an elongated ovate form, and 
shows two or three articular facets; its 
greatest extension is at right angles with 
the greatest width of the head. 
f 28 is a cast of a specimen in the collection 
of J. F. Walker, Esq. It differs more from 
the other specimens than they do among 
themselves, chiefly through the suppression 
of the trochanteroid processes at the prox¬ 
imal end making the head circular, but 
