264 ZOOLOGICAL GEOGRAPHY, [part hi. 



endeavour to ascertain the meaning of this special relation at 

 a subsequent stage of our inquiries. 



Plate V. — River Scene in West Africa, with Characteristic 

 Animals. — Our artist has here well represented the luxuriance 

 and beauty of a tropical forest ; and the whole scene is 

 such as might be witnessed on the banks of one of the 

 rivers of equatorial West Africa. On the right we see a 

 red river-hog {Potamochcerus penicillatus), one of the hand- 

 somest of the swine family, and highly characteristic of the 

 West African sub-region. In a tree overhead is the potto 

 (Perodicticus potto), one of the curious forms of lemur con- 

 fined to West Africa. On the left is the remarkable Pota- 

 mogale velox, first discovered by Du Chaillu, — an Insectivorous 

 animal, with the form and habits of an otter. On the other 

 side of the river are seen a pair of gorillas {Troglodytes gorilla), 

 the largest of the anthropoid apes. 



The bird on the wing is the Whydah finch ( Vidua paradisea), 

 remarkable for the enormous plumes with which the tail of the 

 male bird is decorated during the breeding season. The crested 

 bird overhead is one of the beautiful green touracos {Turacus 

 macrorhyncJms), belonging to the Musophagida?, or plantain-eaters, 

 a family wholly African, and most abundant in the western 

 sub- region. 



■ Reptiles. — In this class we find a large number of peculiar 

 forms ; 13 genera of snakes, 3 of lizards, and 2 of tortoises being 

 confined to the sub-region. The snakes are Pariaspis, Elapops, 

 and Prosymna (Calamariidae), Rhamnophis, Herpetethiops, and 

 Grayia (Colubrida?), Neusterophis and Limnophis (Homalopsidae), 

 Simocephalus and Holurophis (Lycodontidae) ; Pelophilus (Pytho- 

 nidse); Elapsoidca (Elapidse) ; and Atheris (Viperidse). The 

 lizards are Balophia (Lepidosternidse) ; Otosaurus (Scincidaj) ; 

 Psilodactylus (Geckotidee). The tortoises, Cinyxis (Testudinidse) 

 and Tetrathyra (Trionichidse). 



Amphibia. — Of Amphibia, there are 2 peculiar genera of tree- 

 frogs, Hylambatis and Eemimantis, belonging to the Polype- 

 datidse. 



