SHARKS AND RAY-FISHES. 
7 
or at the approach of danger; hut in the generality of Sharks, 
1 not in all, the exposed surface becomes oval by means of a 
skin above and below the globe, which, when the 
fash finds itself hooked on the line, or otherwise in danger, is made 
to close over it, somewhat after the manner of the eyelids in 
ir s. lie globe itself is supplied •with muscles to direct its 
actions, and its sphere of motion is still more extended by means 
VD we see a remarkable instance of the 
bv th J ^ ^ produced 
by the ..mple lengthening on, „f « well-known pen into n new 
[n whlel r “ "t 0“ ‘ho '"ity 
whTch M ’■'1 ' "-0 find ,h., the globe, 
Ute bon of Ibe power of ,i,i„„, U lifted from 
the bottom, on which, m other aninml, bceidee those of this great 
ih 7 ’ ’ 1° “7 “ °° “ ’“o" fbat itself forms 
hoL ** of ’'■•‘ol' “ bned on the 
simakirh '"”'0 P'operly 
b™ , 7 ," ‘“7*'^' •'“» “ >i“lo foo'-"! that it may 
If li!: “ " “O'fi'i'otion of the orhitary process 
liar nib T"'r™, l'*' '">0 holt of this 
lenl S ,h V “'‘"““S' of ‘"0"»8 “ fttoater 
ength ,0 the muscles which mo« the eye, and by so doin- of 
It The lifl “ -ore ondden, as well a, a more eMensive action 
01 the eyes in prowling for their prey. 
arrangement of the teeth in Sharks 
gteat^reTeeTL*:STl 'whlcTr 
deserihhig them and the process by whilh Ibey aTTr'oIeei" 
and also the succession of them continued Tn mly ^ 
fiah they take tbeir ri» from a membrane whiel I, o" 
jawsi-for we exclude the consideration of those which are found 
in the g„l let, tongue, and p.I.to-^and they rUe immediately from 
this foundation m an upright direction T-t 
tached tor a time, and then”, hey M awiv m 7 7 f 
to be succeeded by others. Wi i Z Slmrk”“ 
widely different; and the pattieula,, „f the p„„„ by which 
they are produced li„e been firs, and most extensirely described 
by Mr. Owen; but they had to some extent been observed by 
myself before I had obtained an opportunity of learning them 
from that gentleman s more extensive discoveries. 
