GEOGRAPHICAL DISTRIBUTION 433 



which has been spoken about elsewhere, as also have some other 

 neotropical forms (see vol. iii, p. 437). 



Neotropical Freshwater Fishes (Pisces). A large eel-shaped 

 Lung- Fish (Lepidosiren) is peculiar to South America, and the 

 order (Dipnoi) to which it belongs is only elsewhere represented 

 in Africa and Queensland (see p. 411). 



In ordinary Bony Fishes (Teleostei) the region is extremely 

 rich, and a few peculiar forms require mention. One family 

 (Osteoglossida) is remarkable in the fact that its geographical 

 range closely corresponds with that of the Lung- Fishes, except 

 that it also includes Borneo and Sumatra. One of the neotropical 

 species (Arapaima gigas), abundant in the great rivers of Brazil 

 and the Guianas, is the largest freshwater representative of the 

 order, for it may grow to a length of over 15 feet, and attain a 

 weight of more than 400 Ibs. Some of the neotropical members 

 of the widely distributed Cat- Fish Family (Silurida) are small 

 forms distinguished by their armoured skins. The Electric Eels 

 (GymnoticUe] are characteristic of tropical America. 



Most Sharks and Rays (Elasmobranchii) are typically marine, 

 yet some of the Sting- Rays (Trygonidce) are at home in the great 

 rivers of South America, though the Indian Ocean is the head- 

 quarters of the family. 



Neotropical Land -Molluscs (Mollusca). The Neotropical 

 region is particularly rich in members of this group, the West 

 Indies being especially so, but it is unnecessary to enter into 

 details. One curious negative feature is the complete absence of 

 all members of the family (Limacida) that includes the ordinary 

 Land-Slugs of the Old World, these being replaced by other 

 types. 



Neotropical Insects (Insecta\ Regarding these Wallace 

 makes the following remarks (in The Geographical Distribution 

 of Animals)'. "The Neotropical region is so excessively rich 

 in insect life, it so abounds in peculiar groups, in forms of ex- 

 quisite beauty, and in an endless profusion of species, that no 

 adequate idea of this branch of its fauna can be conveyed by the 

 mere enumeration of peculiar and characteristic groups. . . . The 

 Butterflies of South America surpass those of all other regions 

 in numbers, variety, and beauty; and we find here, not only more 

 peculiar genera and families than elsewhere, but, what is more 

 remarkable, a fuller representation of the whole series of families." 



