128 A HISTORY OF FISHES 



rows parallel with the edges of the jaws, or in rather broad 

 bands or patches (Fig. 46c). All the teeth are, as a rule, more 

 firmly attached than those of the Selachians, although in 

 certain fishes some or all of them are freely movable. Very 

 rarely, as in certain Characins {Characidae, etc.), and in the 

 File-fish {Monacanthus) and Trigger-fish (Balistes), they are 

 implanted in sockets in the bone. The succession is much more 

 irregular, new teeth being formed at the bases of the old ones 

 or in the spaces between them. In size and form they present 

 an extraordinary diversity, the type of dentition being in- 

 timately associated with the nature of the food. 



The teeth on the tongue (Ungual teeth) are borne by the 

 lower elements of the hyoid arch, whilst those inside the mouth 

 are connected with the bones of the primitive upper jaw {i.e. 

 the paired palatines and pterygoids) and with certain other 

 bones developed beneath the floor of the cranium (Fig. 460). 

 The pharyngeal or gill-teeth in the throat are connected with 

 the inner margins of the branchial arches. As a rule, the lower 

 ones are borne on a pair of bones known as the lower pharyn- 

 geals, lying behind and parallel with the lower limbs of the 

 last arch, and representing the remains of a once complete 

 branchial arch (Fig. 54B). The upper pharyngeals are toothed 

 bones representing the upper elements of the preceding arches. 

 In a number of Bony Fishes the lower pharyngeals are united 

 to form a single plate-hke bone, often of characteristic form 

 (Fig. 54A). In the majority of cases the pharyngeal dentition 

 may be said to be inversely proportional to the extent of tooth 

 development in the jaws; that is to say, if the jaws are strongly 

 armed with teeth the pharyngeal teeth are feeble or absent, 

 and vice versa. 



A large number of Bony Fishes are piscivorous (fish-eaters), 

 the stronger preying on their weaker brethren. The teeth of 

 such fishes are generally strong, and may be acutely pointed 

 as in the Cod {Gadu^), Perch (Perca), and Bass (Morone), serving 

 not only to seize but also to tear and dismember the prey. 

 The Pike {Esox) has a large mouth which fairly bristles with 

 teeth, those on the praemaxillaries being small, while those on 

 the sides of the lower jaw are strong and erect, being used for 

 seizing the victims ; those on the roof of the mouth are slender 

 and pointed, arranged in three parallel bands, and instead of 

 being firmly joined to the bones are attached thereto by fibrous 

 or elastic ligaments (Fig. 460). These teeth on the palate are 

 directed backwards towards the gullet, and can be depressed 



