ON THE ANATOMY OF FISHES. 
209 
deflected, bat to a less extent (fig. 88). A very similar lateral outgrowth (figs. 87, 88, 
v.y). ) is also given off on each side from the ridge bounding the aortic groove, which is 
nearly equal in extent and parallel to the more dorsally situated lamina formed by 
the expanded and confluent transverse processes. The anterior margin of each 
ventral outgrowth curves upwards and meets the deflected anterior edge of the 
transverse process of the fourth vertebra, in such a way as to form an anteriorly 
projecting convex surface, which is closely applied to the posterior face of the 
exoccipital and the adjacent portion of the epiotic. These dorsal and ventral 
outgrowths enclose between them, on each side, a relatively spacious recess continuous 
with each other posteriorly beneath the centrum of the fifth vertebra, open laterally 
in the dry skeleton, but closed in the fresh specimen by the lateral cutaneous area of its 
side, and terminating in front in a shallow bony cul-de-sac. At the anterior extremity 
of each cul-de-sac, and on the inner side, near the anterior end of the complex 
centrum, there is a small oval foramen through which the anterior process of the 
tripus passes to its connection with the scaphium by means of the interossicular liga- 
ment. On each side of the commencement of the aortic groove the ventral outgrowth 
is perforated by an oval foramen (fig. 87, sp.n^') for the transmission of the 
rami ventrales of the second and third spinal nerves, which primarily leave the neural 
canal between the exoccipital and the arch of the complex vertejDra, and, after 
traversing the bony cul-de-sac, dorsad to the anterior cornu- of the air-bladder, pass 
to their peripheral distribution through the oval foramen in question. 
The post-temporal (figs. 87, SS, 2 ^t.s., has no obviously distinct inferior limb for 
the usual articulation with the basioccipital, but it is nevertheless possible that the 
strip of bone disposed transversely between the foramina for the exit of the vagus 
(fig. 87, X) and the second and third spinal nerves may represent that element, 
which, presumably, has fused internally with the basioccipital, and posteriorly and 
externally with the conjoined anterior margins of the ventral outgrowth and the 
transverse process of the fourth vertebra. The ascending process (figs. 87, 88, pt.a.) 
is greatly expanded and articulates with the supraoccipital, epiotic, and pterotic 
bones. The stem of the post-temporal (pt.s.) curves obliquely backwards and down- 
wards, and is firmly applied to the distal edge of the decurved anterior margin of 
the transverse process of the fourth vertebra, and to the contiguous distal margin of 
the ventral outgrowth (fig. 88). The distal margin of the confluent transverse 
processes above, and the corresponding margin of the ventral outgrowth below, in 
conjunction with the post- temporal stem in front, form a bony rim which is only 
incomplete behind, and to this rim the peripheral margins of the lateral cutaneous 
area of each side are attached. The socket for the clavicle is a deep groove 
between the post-temporal stem externally and the distal edge of the ventral 
outgrowth internally. 
The air-bladder (figs. 87, 88, a.b., a.h.') is a tubular structure of fairly uniform size 
throughout, and consists of a transverse portion (fig. 87, a.h.) lying across the ventral 
MDCCCXCIII. — B. 2 E 
