488 FISHES. 



ceans, and other small animals disporting themselves on the 

 ground which is left uncovered by the receding water. With 

 the aid of their strong pectoral and ventral fins and their 

 tail, they hop freely over the ground, and escape danger by 

 rapid leaps. The peculiar construction of their eyes, which 



Fig. 221. — Periophthalnms koelreuteri. 



are very movable, and can be thrust far out of their sockets, 

 enables them to see in the air as well as in the water ; when 

 the eyes are retracted they are protected by a membranous 

 eyelid. These fishes are absent in the eastern parts of the 

 Pacific and on the American side of the Atlantic ; but singu- 

 larly enough one species reappears on the West African 

 coast. About seven species are known (including Bohoph- 

 ihalmus), P. hoelreuteri being one of the most common fishes 

 of the Indian Ocean. 



Elboteis. — Body scaly ; eyes of moderate size, lateral, not 

 prominent. Teeth small. Two dorsal fins, the anterior generally 

 with six spines. Ventrals not united, though close together, with 

 one spine and five rays. 



About sixty species are known from the tropics, only a 

 few extending into the temperate zone. As regards form, 

 they repeat almost all the modifications observed among the 

 Gobies, from which they differ only in having the ventral 

 fins non-coalescent. On the whole they are somewhat larger 

 than the Gobies, and rather freshwater than marine species, 

 some of them being abundant in the rivulets of the islands of 



