978 
teeth in both jaws would project forwards in- 
stead of being opposed to one another, and 
such, in fact, must have been their position 
were it not that, as in Pimelepterus, the teeth 
are bent at nearly a right angle with their 
base. In the Scarus, and likewise in the mar- 
ginal teeth of the Diodon, where these organs 
are straight and attached horizontally to the 
margin of the jaws, their sides instead of their 
crowns are actually opposed to each other. 
In the Cod-fish, Wolf-fish, and some other 
species, in proportion as the ossification of the 
tooth advances towards its base and along 
the connecting ligamentous substance, » the 
subjacent portion of the jaw-bone receives 
Fig. 512. 
Portion o 
igamentous attachment of the teeth. 
a, a, a, anterior teeth; b, b, b, posterior teeth in their 
erect position ; c, one of these teeth laid flat towards 
the interior of the mouth, the dotted lines indicating 
its condition when erect. (After Owen.) 
a stimulus and developes a process cor- 
responding in size and form with the so- 
lidified basis of the tooth. In this case the 
inequalities of the opposed surfaces of the 
tooth and maxillary dental process fit into each 
other, and for some time they are firmly at- 
tached together by a thin layer of ligamentous 
substance; but, in general, anchylosis takes 
place to a greater or less extent before the tooth 
is shed. The small anterior maxillary teeth of 
the Angler ( Lophius) are thus attached to the 
jaw, but the large posterior ones remain always 
moveably connected by highly elastic glisten- 
ing ligaments, which pass from the inner side 
of the base of the tooth to the jaw-bone 
(fig. 512, d). These ligaments do not permit 
the tooth to be bent outwards beyond the ver- 
tical position, when the hollow base of the 
tooth rests upon a circular ridge growing from 
the alveolar margin of the jaw; but the liga- 
ments yield to pressure upon the tooth in the 
contrary direction, and its point may thus be 
directed towards the back of the mouth; the 
instant, however, that the pressure is remitted, 
the tooth flies back, as by the action of a 
spring, into its former position. The deglu- 
tition of the prey of this voracious fish is thus 
facilitated and its escape prevented. 
The teeth of the Wolf-fish, Anarrhicus, are 
B nal buttress and of thedome itself iscom 
the jaw of Lophius piscatorius, showing the 
PISCES. 
extremely remarkable. They do not adhere 
immediately to the jaw or to the palate bone, 
but are attached to conical or hemispherical 
osseous epiphyses, which are fixed to these bones 
by a kind of suture, and are easily detached at 
certain periods. The base of each of these 
epiphyses is surrounded with a row of small 
foramina, doubtless intended for the admission 
of vessels, and mark the line of separation. 
On the summit of these cones the true teeth, 
formed as usual of dentine and enamel, are at- 
tached, 
“ If,” says Professor Owen, in the valuable 
treatise from which we have extracted the pre- 
ceding paragraphs, “ the engineer would study 
the model of a dome of unusual strength and 
so supported as to relieve from its pressure 
the floor of a vaulted chamber beneath, let — 
him make a vertical section of one of the 
haryngeal teeth of the Wrasse (fig. 513). 
he base of this tooth is slightly contracted 
and is implanted in a shallow circular cavity, — 
the rounded margin of which is adapted to a 
circular groove in the contracted part of the 
base. The margin of the tooth which thus 
immediately transmits the pressure to the 
bone is strengthened by an inwardly project- 
ing convex ridge. The masonry of this inter- 
of hollow columns, every one of which is 
placed so as best to resist or to transmit in 
a due direction the superincumbent pres- 
sure.” The use of this beautiful piece of 
animal mechanics is to keep the delicate 
successional pulp which is lodged beneath 
the vault of the arched tooth, from being 
injured by pressure during the action of these 
powerful crushing teeth. 4 
Fig. 513. © 
Teeth of the Wrasse ( Crenilabrus). 
Portion of the pharyngeal bone of the Wrass 
a, structure of arched teeth; 6, successional te 
¢, bone. ; 
In Rhizodus, a large extinct spec 
Sauroid fish, the broad base of the too 
divided into a number of long and s! 
cylindrical processes, which are implant 
piles in the coarse osseous substance 
jaw. They diverge as they descend, 
extremities bend and subdivide like the 
of a tree and are ultimately lost in the 
tissue. This mode of attachment of a to 
perhaps the most complicated met with it 
animal kingdom. De. 
In order to complete our remarks concer 
the teeth of Fishes it only remains to notice 
few examples in which the dentition is peculi 
namely, in the Cyprinide, the Scari, the Di 
dons, and the Tetradons. 
ad 
