2 sy Sen DAA eg | wy Fea eit \ 
WK ' in I a vi A Aa ana tlt : ) 
UND Aaa fen Ades aCe aallarah 420 ear mur feels 
oan ee 
ie ; 
-- = = Laks = 4 
Fig. 1. Lower Dentition of the Bony Pike. 
ANIMAL DENTITION. 
By BR. LypDEKKER. 
PART IV. FISHES—(concluded). 
(ae preceding article of this series was devoted to the consideration of the dental 
apparatus of the sharks, rays, chimeras, lung-fishes, and their extinct allies; in 
the present, and final, section we have to consider the teeth of the modern bony 
fishes and thei forerunners the enamel-scaled fishes, of which the great majority 
belong to long-past epochs of the earth’s history. These gronps comprise such an 
enormous number of representatives that anything like a comprehensive survey of the 
various modifications presented by their dentition would obviously be altogether impossible 
in the space at my command, while it is only too hkely that it would prove wearisome 
to my readers. JI shall accordingly confine my observations to some of the more strange 
and remarkable types of dentition, especially those which are of more than ordinary 
interest either from their intrinsic beauty, or from peculiarities in structure, arrangement, 
or situation. 
If we omit their near relations the sturgeons, which have exchanged the polished 
scale armour for a series of bony plates, the only modern survivors of the great group of 
enaimel-scaled fishes are the Bony Pike (Lepidostews) of the rivers of North America, and 
the Bichirs (Polypterus) and Reed-Fish (Calaméichthys) of those of tropical Africa. As 
regards the teeth of these survivors of a lost group, it must suftice to say that in 
the bichir there are two rows of small sharp teeth, of which those in the front row 
are the largest, while the himder ones are rasp-like. The long jaws of the bony pike 
(Fig. 1) are armed with similar pointed and rasp-like teeth, arranged in several rows, 
those of one row being much larger than those of the others, while each tooth is 
separated from its neighbour by the sockets of older teeth which have been shed. 
Teeth of the same general type also occur on the bones of the palate. “Fishes from: 
the Carboniferous formations (Rhizodus) exhibit a somewhat similar type of dentition, 
but, mm correlation with the superior dimensions of the fishes 
themselves, the enlarged teeth were of great size, measuring an yaa 
inch or more in length, and constitutmg formidable weapons of Sy NW } 
offence. ye (ae) 
Of a widely different type from the foregoing is the denti- @ oe (Ni 
tion of the Wealden and Oolitic fishes known as Lepidotus, in 
which the palate was covered with a number of blunt hemi- CW) ) 
spherical teeth evidently adapted for crushing. In the species 
c ( ) Tee 
from the Wealden formation of Kent and Sussex these teeth | WO) 
Shay in 
UN! 
are comparatively small, and the crown forms a distinct although | yy ee 
blunt cone. On the other hand, in the giant Lepidotus Le \ 
(Fig. 2), from the Kimeridge Clay, which is considerably older : tt 
than the Wealden formation, the palatal teeth are much larger Fig.2. Palatal Teeth of the 
dj . Giant Lepidotus, from the 
and flatter, and look like buttons. Not the least curious icimenidae Gla 
287 
