The reptilian fauna exhibits an exceptionally large number of interesting genera and species. A great part of the river systems of the country with their flooded areas are highly favourable to the development of reptilian life. Most prominent among these is the American alligator, of which there are, according to Netterer, two genera and eight species in Brazil. They are very numerous in the Amazon and its tributaries and in the Paraguay, and are found in all the rivers of the Atlantic coast. Three of the Brazilian species are voracious and dangerous. The largest of the Amazon species are the _jacaré-assú_ (_Caïman niger_), _jacaré_ (_C. fissipes_) and _jacaré-tinga_ (_C. sclerops_). The Amazon is also the home of one of the largest fresh-water turtles known, the _Emys amazonica_, locally called the _jurará-assú_ or _tartaruga grande_. These turtles are so numerous that their flesh and eggs have long been a principal food supply for the Indian population of that region. Another Amazon species, the _E. tracaxa_, is still more highly esteemed for its flesh, but it is smaller and deposits fewer eggs in the sandy river beaches. Lagartos (_Iguanas_) and lizards are common everywhere. The ophidians are also numerous, especially in the wooded lowlands valleys, and the poisonous species, though less numerous than others, include some of the most dangerous known--the rattlesnake _surucucú_ (_Lachesis rhombeatus_), and _jararáca_ (_Bothrops_). The Amazon region is frequented by the _giboia_ (boa constrictor), and the central plateau by the _sucuriú_ (_Eunectes murinus_), both distinguished for their enormous size. The batrachians include a very large number of genera and species, especially in the Amazon valley.
The fauna of the rivers and coast of Brazil is richer in species and individuals than that of the land. All the rivers are richly stocked, and valuable fishing grounds are to be found along the coast, especially that of southern Bahia and Espirito Santo where the _garoupa_ (_Serranus_) is found in large numbers. Some of the small fish along the coast are highly esteemed for their flavour. Whales were once numerous between Capes St Roque and Frio, but are now rarely seen. Of the edible river fish, the best known is the _pirarucú_ (_Sudis gigas_), a large fish of the Amazon which is salted and dried for market during the low-water season. Fish is a staple food of the Indian tribes of the Amazon region, and their fishing season is during the period of low water. The visit of Professor Louis Agassiz to the Amazon in 1865 resulted in a list of 1143 species, but it is believed that no less than 1800 to 2000 species are to be found in that great river and its tributaries.