teeth are most y 
ner pteatare Ag 1 es connys pene 
tal i In this fish the 
pavement. 
In the Cestracion Philippii, or Port Jack- 
Shark, both the above descriptions of teeth 
found united in the same jaws, the anterior 
proof of a very convincing descri 
tion that the teeth of Fishes are developed 
animals, where the jaws and teeth are brought 
into closer relation with each other. 
The teeth of the Squaloid Fishes or true 
Sharks are renewed by a very similar mode of 
growth. In these redoubtable monsters of the 
deep the teeth consist of numerous rows of 
broad and trenchant lamine, the anterior row 
of which (fig. 510, a) stands up icu- 
larly from the jaws ready for use, while the 
succeeding layers are recumbent, being covered 
over by a fold of the mucous lining of the mouth. 
Seas penvimelygaial perme a 
ly new sharp rows bei 
constantly ready behind to replace the old and 
worn ones in front as soon as the latter fall out 
or become useless. 
The situation of these teeth and their mode 
of growth is represented in the annexed figure. 
Their only connection with the cartilaginous 
jaw is evidently through the medium of the 
interposed fibro-mucous layer (d), which, as 
it slowly advances , carries the teeth 
with it, and thus brings the successive rows 
gressively into use. In the Sharks there 
1s no distinct pulp, the dense exterior layer 
of the tooth being formed by the calcifi- 
cation of the “membrana propria” of the 
p» so that when divided they are found to 
permanently hollow, as represented in the 
figure (c). ; 
In the Cyclostomatous Fishes the teeth are 
still more evidently mere cuticular appendages, 
seeing that in their case there are no bony 
jaws to which they can be affixed. In the 
Myzine Glutinosa, the Hag-fish, one of the 
most humbly organized but at the same time 
the most formidable of the finny tribes, this is 
extremely evident. The Myxine is generally 
found buried in the substance of some large 
single sharp and recurved attached 
to the centre of the roof of their mouth and 
fixed to the cartilages of the cranium by strong 
which is quite distinct from the cartilaginou 
skeleton, and evidently purely com 
epidermic structures. Ine tesih of foe La 
prey posed of horny plates or tube 
cles of different forms, which are di pe 
mouth, much in the same manner as oth 
<r epidermic structures, and from tt 
isposition will evidently secure a deadly he 
of any victim seized upon. Besides these” 
bial teeth there is one fixed to the roof of 
mouth which is obviously analogous to” 
solitary ine fang of Myxine last deser 
This (fig. 511, 6) 1s composed of two Tor 
cones attached by fibrous ligaments to the p 
tine cartilages in the roof of the mouth. 
fongne (6), which, ike We Sam xu 
is here very moveable and capable of being ® 
tracted and ed by means of stron 
armed with 
«<5 
tears through the flesh of its prey. 
