258 Animal Life 
employed for mastication; on the contrary, this 
function is performed only by certain raised and 
roughened areas, technically known as “tritors.” 
These are well shown in the sketch of a tooth 
of a gigantic fossil member of the group repro- 
duced in Fig. 12, such teeth being very common 
in the Chalk and some of the lower Tertiary 
formations of this country. Chimeras are entirely 
carnivorous fishes, feeding largely on herrings, Fig. 12. Lower Tooth of an extinct Chimera, 
but also eating shell-fish and crustaceans. Pn ee giana 
Perhaps the nearest approach to the type of dentition characteristic of the king- 
of-the-herrings and its relatives is presented by the Lung-Fishes of the present day and 
their extinet predecessors. These strange fishes have only three existing generic 
representatives, namely, the Mud-Fishes of West Africa and tropical South America, and 
the Barramunda, or Dawson River salmon of Queensland. The mud-fishes (which take 
their name from the habit of rolling themselves into balls in the mud when the rivers 
or marshes they inhabit are dried up) are elongated eel-like fishes with whip-like fins. 
The barramunda, on the other hand, is of less peculiar form and proportions. Its 
teeth consist of two pairs of the type of that represented in Fig. 13, one paw being 
situated near the middle of the palate, and the other on the corresponding portion of 
the lower jaw. In addition to these, there is a pair of much smaller and simpler 
teeth near the front of the palate. The two large teeth in each jaw are placed side 
by side, with the ridges (rom which the genus derives its name of Ceratodus) projecting 
outwards. Not the least interesting fact connected with these curious teeth is that 
they were known for many years only as fossils, and that it was not till well on in 
the second half of the last century that a living representative of the group turned 
up in the rivers of Queensland. This discovery served to confirm the conclusions 
deduced from their associated remains as to the fossil teeth belonging to fresh-water 
fishes, and also proved—what could not have been otherwise ascertained—that these 
fishes are herbivorous, the Queensland species feeding chiefly on the decomposing foliage 
of plants growing on the banks after it has fallen into the rivers. That teeth of the 
type under consideration should belong to herbivorous fishes, while those characteristic 
of the king-of-the-herrings are associated with carnivorous habits, shows indeed that no 
definite conclusions can be drawn from many kinds of fossil fish-teeth as to the nature 
of the food of their owners. 
Extinct generic types of lung-fishes abounded during the earlier epochs of the 
earth’s history, especially at and about the time when the forests from which our 
coal is formed were growing. In all of these the teeth were of the same general type 
as those of the barramunda (of which 
representatives even then were in existence), 
but in many of them the ridges on the 
erinding surfaces were more numerous, and 
in certain instances provided with comb-like 
processes. From this comb-like structure the 
name of Otenodus (comb-tooth) has been 
assigned to those coal fishes of which the 
teeth are shown in Fig. 14. 
The present article may be brought to a 
close with a brief mention of the teeth of the 
fish-like creatures known as Hag-Fishes and i Se et 
3 i ig. 13. A Tooth of a fossil Barramunda. c. Point 
Liampreys, which are worm-like in form, of contact with the opposite Tooth. 
SS 
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