112 
ICHTHYOSAURI A FROM THE 
Case. Shelf. Specimen. 
1 c vertebral nerve is not large. After the third 
all the cervical vertebrae have the ventral 
side rounded, and differ from each other 
chiefly in size. 
3—21 cervical vertebrae, in which the only noticeable 
change is, that the pit for the neurapophysis 
comes to look more and more outward. 
I d 
d 
d 
d 
1 the last cervical or pectoral vertebrae, and the 
first dorsal. In the former the upper head 
for the rib will be seen to be partly on the 
centrum, while in the succeeding vertebrae 
both tubercles are for the first time entirely 
on the centrum. 
2 four early dorsal vertebrae, showing the rapid 
descent of the upper tubercle for the rib 
down the side of the centrum. 
3—5 early dorsal, the ventral part of the centrum 
between the tubercles still convex from side 
to side. 
6—17 mid and late dorsal, in which the outline of the 
centrum becomes sub-hexagonal, the ventral 
surface flattened, and the approximating 
tubercles are at the base of the side. 
I e 1 late dorsal. 
2 last dorsal; on one side the rib-tubercles are 
distinct, on the other side they are welded 
into one oblique tubercle directed downward 
and forward. 
e 3—18 early caudal, differing but little in characters, 
though the later vertebrae have the centrum 
a little smaller, and the early vertebrae have 
the tubercle for the rib elongated instead of 
ovate. In outline they are sub-quadrate 
with the corners taken off. 
/ 
1—3 early caudal. 
4—12 late caudal; more quadrate in outline, with 
the intervertebral cup less deep than in the 
