LAND REGIONS. 19t) 



those of the Mexican Province, belong to the Ciictus Region of 

 botaiiists, and have a mean temperature of 68 -^ to 84°. Land 

 shells are abundant in the forests and underwood of the lower 

 zone of the mountains, where the temperature is 10° less, and 

 the rains more copious. These diverse countries are characterized 

 by the abundance of bulimiform shells, Bulimus, Bulimulus, 

 Otostomus, Orthalicus, etc ; of the operculated genus of Cyclotus, 

 including some fine, large species, and of AmpuUaria. The 

 heliciform groups Labyrinthus, Isomeria and Solaropsis are 

 numerous. Finally, the following characteristic genera occur : 

 Guestieria, Rhodea, Bourcieria, Mulleria. The American Clau- 

 silifB are represented by a few species, but their metropolis is 

 the Peruvian Region. There are a few Streptaxis — a Brazilian 

 genus, several species of which, nevertheless, occur in the tropical 

 countries of Asia and Africa. The genus Mulleria, which lives 

 in the Rio Magdalena may be considered the analogue of the 

 fresh-water 03^ster JEtheria of Africa. The Melanians mostly* 

 belong to Hemisinus, a South American group extending into 

 Brazil, and having its northern limit in the West Indies. 



25. Brazilian Region. 



" The region of palms and melastomas," extending from the 

 Amazon to the southern tropic, is one of the richest zoological 

 provinces ; it includes Brazil and the districts of Peru, Ecuador 

 and Bolivia east of the Andes. A large part of the region is 

 mountainous and rainy and densely wooded, but intersected by 

 extensive plains ( Llanos > ; some grassy and fertile, others dry, 

 rock}" and rainless — especially in the South. It is watered by 

 numerous streams — the affluents of the Amazon and Plata. 



The dominant character of the molluscan fauna is the import- 

 ance of bulimiform snails, and the contrasting scarcity of the 

 heliciform types ; thus of about 300 species of terrestrial and 

 fluviatile shells of the region, the Bulimi number 108, the Helices 

 only 14. The principal forms are : Streptaxis It sp., Anostoma 

 4 sp.; Helix, of sections Ophiogyra, Solaropsis, Geotrochus, 

 Labyrinthus; Bulimus, of sections Macrodontes, Odontostomus, 

 Tomigerus, Pelechilus, Anthinus, Pachyotus, Strophochilus, 

 Borus, Orphnus, Otostomus, Liostracus, Anctus, Eudioptus, 

 Rhinus ; Peltella; Simpvilopsis ; Megaspira ; Obeliscus ; Dorissa; 

 Hemisinus ; AmpuUaria ; Hyria ; Castalia ; Leila. 



The interior streams contain but few gastropod mollusks. 

 There are Ancylus 3, Physa 1, Doryssa 3, Hemisinus 11, Melania 

 6, AmpuUaria 18, Neritina 2. The Unionidse, etc., number 

 nearly 50 species, including the South American genera Hyria, 

 Mycetopus, Castalia, Leila, Monocondyloea. Besides the group 

 Borus, containing the largest species of Bulimi, the other 



