CAMBRIDGE UPPER GREENSAND. 
59 
outline, which decreases in size posteriorly. 
The two lower sides are rounded and 
round into each other at the base. The 
heads for the ribs are wide apart; on the 
left side the lower tubercle is seen on the 
atlas near the suture. 
An associated basi-occipital and atlas and 
axis, reputed to have been found with the 
specimen in Case ix. e ,f . p, but differing 
in mineralization. The basi-occipital is of 
the large type, with the ex-occipital facets 
cutting off the anterior part of the neural 
canal; it is wide transversely in front of the 
condyle. The atlas and axis much resem¬ 
ble the specimen 6.1; but while this spe¬ 
cimen is smaller than that, it is of greater 
antero-posterior length. The posterior cap 
is relatively smaller and deeper. The lower 
bosses for the ribs run a line through the 
vertebra above the central depression of 
the posterior cup, instead of through it as 
in specimen b . 1, or below it as in speci¬ 
men b . 2. 
b 5—6 An associated basi-occipital and basi-sphe- 
noid, presented by C. Montagu Doughty, 
Esq., as part of the Doughty Collection. 
The basi-occipital is of the type of the 
species a . 3; it has the ex-occipital facets 
parallel with the neural canal and below 
it. The condyle is made circular by 
deep grooves at the sides, which make a 
crescent-shaped part on each of its sides: 
mesially the condyle has a short vertical 
ligament-marking in its upper half. An¬ 
teriorly the bone is sub-hemispherical, in¬ 
stead of being flat at its junction with the 
basi-sphenoid. 
The basi-sphenoid is of the usual form, 
Case. Shelf. 
X b 
No. 
3—4 
