29 
Appendicular Skeleton. — Of the paired fins, the pelvics appear to have 
been the most powerful, and the pectorals are only represented in one specimen 
(No.y) hy an imperfect fragment. As shown by No. c, each pelvic fm con- 
sists of at least twenty stiff rays, articulated at distant intervals ; and, if this 
sj)ccimcn is not deceptive, the appendage has a gently rounded free margin, 
the rays gradually diminishing in length both in front and behind (PI. IX, 
Pig. 3, and PI. X, Pig. 4) . It is also, perhaps, noteworthy that in tlie originals 
of PI. IX, Pig. 3, and PI. X, Pig. 4, there is a considerable vacant space 
between the base of the dermal rays and the trunk. 
The median fins are rarely well jii’eserved, but, so far as known, they 
differ little in form and proportions from those of B. gigas. Tfie large intcr- 
sjoinous bones supporting the dorsal and anal fins are well shown in the 
originals of PI. IX, Pigs. 3 and. 4, where they, perhaps, correspond in number 
with the neural and lucmal spines, but are mucfi fewer than the fin-rays ; 
the latter are at least fifty in number in the dorsal fm, and they are all much 
flattened, apparently articulated though not lirancfiing, and closely arranged. 
Exoskeleion of Trunk. — Like the other species of the genus, B. gracilis 
possesses four longitudinal series of dermal scutes — a median dorsal and a 
median ventral of equal size, and a row of smaller scutes on each side 
supporting the canal of tlie lateral line. Eacli of the dorsal and ventral scutes 
(PI. VIII, Pigs. 5, d.s., V.S.; PI. IX. Pigs. 3 and 4; PI. X, Pig. 4) is longer 
than broad, the anterior margin having a deep triangular excavation, and the 
posterior margin being acutely pointed, though somewhat rounded laterally. 
The anterior border of one scute is overlapped, as usual, by the jiosterior 
border of the one immediately in front ; and the external surface of eacli 
evidently exhibits a low longitudinal keel, though traces of superficial 
tuberculations arc only discernible in one specimen. No. g. It is also 
interesting to observe that in one fossil (PI. X, Pig. 4) there is an appearance 
of bifurcation of the ventral series of scutes in the region of the pelvic fins, 
resembling the loop-arrangement surrounding the “anal-grube” in B. strio- 
latus (PI. X, Pig. 5) already made known by Kner.* 
Remarks . — This species is distinguished from its nearest known allies, 
B. gigas and B. macroceglialiis, by the form of the scutes and the relatively 
greater elongation of the trunk. 
* R. Kner, Sitzungsb. math. -natur. Cl. k. Akacl. Wiss., ISC6, Vol. liii, Pt. i, p. 194, PI. vi, fig. y. The 
present Writer has been al)le to confirm this determination by an e.xamination of the original specimens in tlie 
<ieol. Keichsanstalt at Vienna. 
