CAMBRIDGE UPPER GREENSAND. 
53 
ICHTHYOSAURI A 
FROM THE CAMBRIDGE GREENSAND. 
The remains of Ichthyosaurs have been less perfectly 
collected than those of any other order of reptiles; so that, 
although these animals were the most abundant of the verte- 
brata, the collections are small, and illustrate but imperfectly 
the correlation of characters in species. 
These bones are contained in Cabinets IX. X. and in 
drawers of Compartment f of the Table-case J. They com¬ 
prise about 870 specimens, of which more than 400 are teeth. 
These fossils, more than others, have come to the Museum 
as isolated specimens; so that the collection is rich in ex¬ 
amples of bones like the basi-occipital, every one of which 
must have belonged to a separate animal. There are also 
series of bones which have been found associated together; 
and these have been preserved associated, and mounted, to 
accumulate materials for determining the characters of spe¬ 
cies. The isolated bones have been put together chiefly in 
Cabinet X. to illustrate the osteology of the genus during 
the aera of the Cambridge Greensand. In Cabinet IX. are 
examples of the associated sets of bones, almost exclusively 
vertebrae. In one of these sets nearly 50 vertebrae were 
found, but the majority were badly preserved. 
In Cabinet J, Compartment f, the specimens are partly 
osteological, illustrating teeth, vertebrae, and the smaller 
bones of the paddle; and partly associated sets, making, 
