246 FISHES CHAP. VIII 
Teleostei, but even these may be absent, and the dermal fin-rays 
then articulate directly with the basipterygium. Little is known of 
the skeleton of the pelvic fins in the fossil Crossopterygu, but there 
is evidence of the existence of a higher 
grade of structure than in their surviving 
allies. In Husthenopteron,’ for example, 
the fin is supported by an axis of at least 
three bony segments, with at least three 
ossified preaxial radiala; hence, it has 
obviously undergone less degeneration than 
in Polypterus, where the fin-skeleton is 
essentially Teleostean. In the Dipnoi the 
pelvic fins are similar to the correspond- 
ing pectoral fins, but individual variation 
: is more marked and even the central 
axis may divide” In the males of all 
a : existing Elasmobranchs, including the 
Va Holocephali, certain of the more distally 
Fic. 149.—Skeleton of the Situated metapterygial radialia become 
left pelvic fin of a Trout modified to form a supporting skeleton 
(Salmo jfario), seen from 
the dorsal surface. B.PTG, for the copulatory organs, the claspers, 
ce eee sf a or mixipterygia. In the latter group 
distal radialia. (From the anterior claspers are also provided 
pon aneeeeyel) with cartilaginous supports articulating 
with the pelvic girdle directly in front of the pelvic fins. 
PTG 
p 
i 
1 Traquair, Geol. Mag. vii. 1890, p. 15 ; Goodrich, 7.c. 
2 Haswell, Proc. Linn. Soc. N.S. W. ix. 1884, p. 71; Howes, P.Z.S. 1887, p. 3. 
