NEOTROPICAL REGION. 237 



America. But with them there came a remarkable North 

 American type, Lepidosteus. Zepidosteus viridis, which is 

 found in the United States, has penetrated on the mainland 

 to the Pacific coast of Guatemala, where it is common at the 

 mouth of the rivers and in brack-water lakes along the coast; 

 it probably crossed iato Cuba from Florida. A perfectly iso- 

 lated type of fishes inhabits the subterranean waters of the 

 caves of Cuba (two species of Lucifuga). The eyes are absent 

 or quite rudimentary, as in most other cave animals. Singu- 

 larly, it belongs to a family (Ophidiidce), the members of 

 which are strictly marine ; and its nearest ally is a genus, 

 Brotula, the species of which are distributed over the Indo- 

 Pacific Ocean, one only occurring in the Caribbean Sea. This 

 type must have witnessed all the geological changes which 

 have taken place since Cuba rose above the surface of the sea. 



A similar mixture of forms of the Tropical and Temperate 

 types of Freshwater fishes takes place in the south of South 

 America ; its details have not yet been so well studied as in 

 the north ; but this much is evident that, whilst in the East 

 Tropical forms follow the Plate river far into the Temperate 

 region, in the West the Temperate Fauna finds still a congenial 

 cUmate in ranges of the Andes, situated close to, or even 

 north of, the Tropic. 



Like the Indian region, the Tropical American has a pecu- 

 Kar Alpine Fauna, the Freshwater fishes of which, however, 

 belong to the Siluroids and Cyprinodonts. The former are 

 small, dwarfed forms (Arges, Stygogenes, Brontes, Astrohlepus, 

 TricJuymyderus, Bremophilus), and have a perfectly naked 

 body, whilst the representatives in the lowlands of, at least, 

 the first four genera are mailed. The Alpine Cyprinodonts, 

 on the other hand, (Orestias) exceed the usual small size of 

 the other members of this family, are covered with thick 

 scales, but have lost their ventral fins. Some of these Alpine 

 forms, like Trichomyderus, foUow the range of the Andes far 



