134 
FISHES OF THE CHALK. 
to belong to a species of Squalus ; a supposition by 
no means improbable. It is not unlikely that the 
large thick, radiated, fin-like processes, hitherto 
referred to the Balistes, are also referable to that 
universally prevailing genus, the Shark. * 
Balistes. — The fishes of this curious genus 
have the head compressed, and close to the body, 
appearing as if it were a continuation of the trunk. 
The mouth is narrow, the teeth in each jaw are 
eight in number, of which the two anterior ones 
are the longest ; there are also three interior ones 
on each side, opposite the intervals between the 
external row. The aperture of the gills is narrow, 
destitute of opercula, and placed above the pectoral 
fins ; the branchiostegous membrane has two rays. 
The body is compressed, and carinated on each 
side ; the scales are coriaceous, joined together, 
and rough, with sharp minute prickles. They 
have two dorsal fins, of ivhich the anterior one is 
alined with a strong spinous ray, concealed in a 
deep groove in the hack, and can he erected or de- 
pressed hy the animal at pleasure.^ Some species, 
as the B. monoceros (Unicorn file-fish), are fur- 
nished with a spine between the eyes. 
The sjDecimen delineated is evidently the de- 
fence of a fish, and so strikingly resembles the 
spine fixed between the eyes of certain species of 
Balistes, that there can be no hesitation in con- 
sidering it to belong to a fish of that genus. It 
is of a dark chocolate colour, and possesses a fine 
* Some years since, a block of chalk, containing upwards of a 
luindred of these bodies, was discovered by the workmen in Offham pit ; 
it was sold to a stranger. 
t Nouveau Diet. d’lTist. Nat. tom. xi. p. 515. 
