CHONDROSTEIDiE. 
27 
in its sheath ; and the peripheral arches are only imperfectly calci¬ 
fied. The neural arches are stout and each pedicle (PL I. fig. 4, 
n.a .) is separate both from its fellow of the opposite side and from 
the long neural spine ( n.s .). No traces of ribs have been observed, 
and robust haemal arches have only been seen at the base of the 
lower caudal lobe. 
The pectoral arch closely resembles that of Acipenser. The post¬ 
temporal (figs. 3, 4, p.t .) is a small, narrow triangular bone, 
overlapped at its attenuated anterior end by the supratemporals. 
The long narrow supraclavicle (figs. 3, 6, s.cl.) is obliquely crossed 
near its upper extremity by the lateral line. The clavicle (PI. I. 
fig. 5, cl.) is sharply bent, with a lower limb and an inner laminar 
expansion as in Acipenser. The infra clavicle (i.cl.) is relatively 
small and trapezoidal. The pectoral fin-supports are unsatis¬ 
factorily known. The pelvic fin-supports, so far as preserved, are a 
single regular series of stout, elongated cartilages, much fewer 
than the dermal rays; but a double series occurs both in the dorsal 
and anal, the baseosts being short, and the axonosts much elongated, 
extending almost or quite to the neural and hsemal spines of the 
axial skeleton. 
The large fulcral scales at the base of the upper caudal lobe are 
supported by a distinct series of vertically elongated cartilages above 
the neural arches. 
Chondrosteus acipemseroides, Egerton. 
[Plate I. figs. 1-5.] 
1844. Chondrosteus ciccipenseroides, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. 
p. 280 (name only). 
1858. Chondrosteus acipenseroides, Sir P. Egerton, Phil. Trans, p. 871, 
pis. lxvii., lxix., pi. lxviii. fig. 2. 
1858. Chondrosteus crassior, Sir P. Egerton, ibid. p. 883, pi. lxviii. 
fig. 1, pi. lxx. [Head ; British Museum.] 
1887. Chondrosteus acipenser oides, 1L H. Traquair, Geol. Mag. [3] 
vol. iv. p. 248, woodc. figs. 1-5 (reprinted in Proc. Boy. Phys. Soc. 
Edinb. vol. ix. p. 349, with woodcuts). 
1887. Chondrosteus acipenser oides, J. W. Davis, Quart. Journ. Geol. 
Soc. vol. xliii. p. 605, pi. xxiii. 
1889. Chondrosteus acipenser oides , A. S. Woodward, Proc. Geol. Assoc, 
vol. xi. p. 36, woodc. figs. 8-12. 
1889. Chondrosteus acipenser oides, M. Browne, Trans. Leicester Lit. & 
Phil. Soc., n. s., vol. ii. pt. i. p. 17, pis. i., ii. 
Type. Imperfect fish ; British Museum. 
The type species, usually attaining a length not exceeding one 
metre. Maximum depth of trunk contained about five and a half 
