338 
KAMAKICHI KISHINOUYE: 
together so firmly that the vertebral column allows little motion to either side. 
The free lateral motion of the vertebral column is possible only at the root of 
the caudal fin, where two vertebrae (the last but one and its antecedent) are 
remarkably thin, and their neural and haemal spines are long, diverging, and 
flattened at the root. Generally the number of the precaudal vertebrae is nearly 
equal to that of the caudal. The vertebrae are 18 + 21 in the Thunnidae, 20 
+ 21 in the genus Katsuwonus, and in the other genera of the Ivatsuwonidae 
20 + 19. The relative number of the precaudal and caudal vertebrae is often mis¬ 
taken, as the haemal spine is also very well developed in the precaudal vertebrae. 
Moreover, it is remarkable that the haemal spine of some anterior precaudal 
vertebrae is turned forward in the Thunnidae (figs. 49-52, 64). In Auxis the 
epihaemal spine is also turned forward in the caudal region too. Thus 
Kcdsuwonus has the same number of caudal vertebrae as the Thunnidae, and 
the number of the precaudal vertebrae does not differ from that of the other 
genera of the Katsuwonidae. In Gunther’s catalogue less numbers of vertebrae 
are recorded ; but tliis I am inclined to believe to be erroneous. Vertebrae 
differ greatly in shape and structure in the different parts of the body. They 
are much modified near both extremities of the body ; but they are com¬ 
paratively simple and light at the middle. It is noteworthy that the haemal 
spine is very well developed in some precaudal vertebrae too, so that when 
ribs are detached it is rather difficult to distinguish them from caudal vertebrae. 
However the haemal spine of the precaudal vertebrae is broad, thin and laterally 
c.impressed at the distal end, for the attachment of ribs, and it is of course 
shorter than that of the anterior caudal vertebrae. It must be noticed also 
that the haemal spine of some anterior precaudal vertebrae is tinned forward 
(figs. 49-52). Each vertebra has a pair of short pointed lateral apophyses at 
the anterior margin of the insertion of the intermuscular bone, especially w r ell 
developed in the caudal vertebrae. These apophyses serve to keep the inter- 
musculars fast to the vertebrae. The four pairs of zygapophyses are well 
developed, of which the superior prezygapophyses are best developed. In the 
Thunnidae the transverse process is well developed in some precaudal vertebrae 
(figs. 13, 49-52, 64). On the dorsal surface of these transverse processes, the 
head of the intermuscular bones and ribs are inserted close together, the former 
preceding the latter. The haemal canal is narrow in Thunnus and Parathumus ; 
