610 THE LIVING ANIMALS OF THE WORLD 



African species is perhaps the better known of the two. On the approach of the dry season it 

 buries itself in the mud at the bottom of the river, and when the latter becomes dry the mud 

 hardens, holding the fish a prisoner till the return of the wet season several months later. A 

 considerable number of these fishes have from time to time been dug out and sent to England 

 enclosed in the mud into which they had retreated. The writer remembers assisting in the 

 liberation of some during the last meeting of the British Association at Oxford. So hard had 

 the prison-walls become that the mass had to be plunged into tepid water; this soon brought 

 about a dissolution of the soil, and in a short time the fishes were swimming about as if in 

 their native rivers. The African lung-fish is known also as the MUD-FISH ; its American relative 

 as the LEPIDOSIREN, or SOUTH AMERICAN MUD-FISH. In the American species, as in its African 

 relative, the fins are whip-like in form ; but the hinder or ventral pair, which correspond to 

 the hind limbs of the higher vertebrated animals, are remarkable in that in the male they 

 develop during the breeding-season numerous thread-like processes, richly supplied with blood, 

 the function of which is as yet unknown. 



The young, both of the African and South American mud-fishes, bear external gills closely 



resembling those of the tad- 

 poles of the frog and other 

 Amphibia; traces of these 

 gills remain throughout life 

 in the African form. 



CHIMERAS 



Shark-like in their 



**^.- , ^^^^^ general characters, the 



^ ";_ A. . J "^^ik CHIM/ERAS, now briefly con- 



JJBSJ .- -' sidered, are nevertheless 



regarded as constituting a 

 very distinct group of great 

 antiquity. 



The modern representa- 

 tives of the group are few in 

 number five species in all. 

 Of these, the species shown in 

 the accompanying photo- 

 graph and the SEA-CAT are remarkable for the possession of a movable tentacle on the snout. The 

 under surface of this tentacle is armed with small spines, and fits into a hollow in the head. 

 The first back-fin is supported in front by a strong spine, and can be depressed into a sheath 

 in the body-walls. The teeth take the form of large plates closely united with the jaws, and 

 studded with hardened points, or " tritors." 



One species widely distributed in the Mediterranean and Atlantic is taken usually in deep 

 water ; it is the largest living species, often attaining a yard in length. Its occurrence is, 

 however, very erratic, months elapsing without any being taken ; at other times several will 

 be caught in a few days. A closely allied fish is often exposed for sale in the Lisbon markets, 

 where it ranks with the Sharks as a food-fish. 



The egg of the BOTTLE-NOSED CHIM/ERA is perhaps the only egg with a mimetic resemblance 

 to a foreign object. It is elliptical in form, and bordered by a fringe, so as to present a close 

 resemblance to a piece of seaweed. 



In the next chapter we begin the description of the great group of Fan- and Fringe-finned 

 Fishes, which, briefly, embrace all fishes not grouped among the Lung-fishes, Chimasras, or 

 Sharks. The anatomical characters used for the purpose of classifying this great group are 

 not discussed here, save only in a few cases of prime importance, when features such as can 

 readily be observed, without demanding an intimate knowledge of anatomy, are selected. 



Phttt b; A. S. Rudland 8 Smi 



BOTTLE-NOSED CHIMERA 



The remarkable structure in front of the mouth is probably an organ of touch 



