CAMBRIDGE UPPER GREENSAND. 
71 
Case. Comp. Drawer. Specimen. 
J f v 1—25 position of the upper tubercle for the 
rib in Cretaceous Ichthyosaurs the 
neck is not always easily distinguished 
from the back in worn specimens. The 
centrum enlarges in size in passing back¬ 
ward from the head, becomes longer 
from back to front, and exchanges 
the sharp mesial angle made by the 
haemal surfaces for a regular semi-cir¬ 
cular outline. 10—17 are dorsal verte¬ 
brae ; 10—12 early dorsal, 13—15 mid¬ 
dorsal, 16, 17 late dorsal. 18—24 are 
caudal vertebrae. 25 is a femur. 
Drawers VI., VII., VIII., IX. of Compartment f of Cabinet 
J are at present unfilled. 
J f x 1—4 Examples of early cervical vertebrae 
mounted to exhibit the form, size, and 
position of the tubercles for the ribs, 
especially the large upper head confluent 
with the neural arch and the small tuber¬ 
cle below. In No. 2 the lower tubercle 
is so small that it might be overlooked. 
Early cervical vertebrae usually have a 
somewhat heart-shaped form. 
J f x 5—7 Early, middle and late dorsal vertebrae. 
The two tubercles for the ribs will be 
seen to descend on the side of the cen¬ 
trum in passing from the pectoral to 
the pelvic region, and with this change 
comes a corresponding change in the 
outline of the cup for the intervertebral 
substance, the cup being always widest 
from side to side between the tubercles 
for the ribs. 
