_Fresh-water fish._--Since the British Museum catalogue was published, a valuable paper by Dr. Günther, in the Transactions of the Zoological Society for 1868, furnishes much additional information on the fishes of Central America. In that part of the region south of Mexico, 106 species of fresh-water fishes are {55}enumerated; and 17 of these are found in streams flowing into both the Atlantic and Pacific Oceans. On the whole, 11 families are represented among the fresh-water fish, and about 38 genera. Of these, 14 are specially Nearctic,--_Amiurus_ (Siluridæ); _Fundulus_ (Cyprinodontidæ); _Sclerognathus_ (Cyprinidæ); and _Lepidosteus_ (Ganoidei). A much larger number are Neotropical; and several Neotropical genera, as _Heros_ and _Poecilia_, are more largely developed here than in any other part of the region. There are also a considerable number of peculiar genera;--_Petenia_, _Theraps_, and _Neotrophus_ (Chromides); _Ælurichthys_ (Siluridæ); _Chalcinopsis_ (Characniidæ); _Characodon_, _Belonesox_, _Pseudoxiphophorus_, _Platypoecilus_, _Mollienesia_, and _Xiphophorus_ (Cyprinodontidæ). A few peculiar Antillean forms are also present; as _Agonostoma_ (Mugilidæ); _Gambusia_ and _Girardinuus_ (Cyprinodontidæ). The other families represented are Percidæ (1 genus); Pristopomatidæ (2 gen.); Gobiidæ (1 gen.); Clupeidæ (2 gen.); and Gymnotidæ (1 genus). On the whole the fish-fauna is typically Neotropical, but with a small infusion of Nearctic forms. There are a considerable proportion of peculiar genera, and almost all the species are distinct from those of other countries. The predominant family is that of the Cyprinodontidæ, represented by 12 genera; and the genus _Heros_ (Chromidæ) has here its maximum development, containing between thirty and forty species. Dr. Günther considers that a number of sub-faunas can be distinguished, corresponding to some extent, with the islands into which the country would be divided by a subsidence of about 2,000 feet. The most important of these divisions is that separating Honduras from Costa Rica, and as it also divides a very marked ornithological fauna we have every reason to believe that such a division must have existed during the latter portion of the tertiary epoch. We shall find some farther evidence of this division in the next class.