Animal Dentition 
corresponding portion of the lower jaw, this dental plate becoming “eh 
very large in the second of the two genera, where it is divided into aa) EI EAG 
two halves by a median cleft. The most remarkable feature about (S)~@ 
these teeth is, however, their structure, since they consist of a vast ee 
number of very thin plates superimposed upon one another somewhat  \® ©) 
obliquely, so that their edges are exposed upon the grinding surfaces. POS 
In these teeth the uppermost plates are, of course, the oldest. Globe- rs 
fishes feed largely upon coral, the branches of which their dentition Gy 
is admirably adapted to break off and crush. The allied genus Triodon 
is intermediate between the other two so far as its dentition is con- jig. 5, Palatal Den- 
cerned, the upper jaw-tooth being divided, while the lower one is single. tition of another 
The huge Sun-Fishes, which are nearly allied to the globe-fishes Eee 
and have a dentition of somewhat similar type, claim special notice 
on account of the circumstance that teeth are also developed on the bony arches by 
which the gills are supported, as shown in Fig. 7. In this connection it may be 
mentioned that up to a few years ago the largest known sun-fish was a specimen in 
the British Museum, taken off the Dorsetshire coast in 1846. Its length is 74 feet. 
This specimen is, however, largely exceeded in size by one captured off Redondo, 
California, which is reported to have measured 8 feet 2 inches in length and to have 
weighed nearly 1,800 lbs. 
Distant allies of the globe-fishes, the File-Fishes (Balistes) of 
the tropical seas have an altogether distinctive and peculiar type 
of dentition, in which the large teeth are limited to the jaws and 
the pharyngeal bones. In the upper jaw (Fig. 8) there are seven 
pairs of teeth arranged in two rows—four in the front and three 
in the hind row. The lower jaw carries only four pairs, corre- 
sponding to those of the front row of the upper one. In form 
these front teeth are somewhat triangular cones, and have their 
anterior surfaces coated with an enamel-like substance of a yellow 
colour. The second row of upper teeth are thin and shaped 
somewhat like the blade of a spoon; when partially worn they 
present some resemblance to unusually thin and broad upper 
human incisors, having a beautifully-polished external surface. A 
constant succession of both series of these teeth is maintained, so that if the bone 
of the jaws be cut open a number of successional teeth will be seen in their 
sockets destined, in course of time, to replace those in use. The pharyngeal teeth form 
small, laterally-compressed, curved and sharp-pointed cones, regularly arranged in two 
rows upon the opposing margins of the two pairs of supporting bones. The file-fishes, 
many of which are beautifully coloured and marked, feed on corals and molluscs, 
breaking off large pieces from the branching species of 
the former organisms with their front teeth, or chiselling 
holes into the shells of the latter with the same efficient 
implements. They do much damage to the mother-of- 
pearl fisheries by destroying the pearl-oysters in this 
manner. 
Since I am not treating the subject in anything 
approaching a systematic manner, and merely select note- 
worthy types without reference to their zoological affinities, 
I make no apology for turning suddenly to a very different 
eroup of fishes, as represented by the Sea-Breams (Dentez). 
The name ‘“ Sea-Bream,” it should be mentioned, must not Vig. 7. GillTeeth of Sun-Fish. 
EOS 
(I 
A, 
Fig. 6. Dentition of a 
Globe-Fish (Tetrodon). 
