=Catalogue of Fishes of Panama.=--In an enumeration of the fishes of the Pacific coast in 1885,[58] the present writer showed that Dr. Günther's conclusions were based on inadequate data. In my list 407 species were recorded from the Pacific coast of tropical America--twice the number enumerated by Dr. Günther. Of these 71 species, or 17-1/2 per cent., were found also in the Atlantic. About 800 species are known from the Caribbean and adjacent shores, so that out of the total number of 1,136 species but 71, or 6 per cent. of the whole, are common to the two coasts. This number does not greatly exceed that of the species common to the West Indies and the Mediterranean, or even the West Indies and Japan. It is to be noted also that the number 71 is not very definitely ascertained, as there must be considerable difference of opinion as to the boundaries of species, and the actual identity in several cases is open to doubt. This discrepancy arises from the comparatively limited representation of the two faunas at the disposal of Dr. Günther. He enumerates 193 marine or brackish-water species as found on the two coasts, 59 of which are regarded by him as specifically identical, this being 31 per cent. of the whole. But in 30 of these 59 cases I regard the assumption of complete identity as erroneous, so that taking the number 193 as given I would reduce the percentage to 15. But these 193 species form but a fragment of the total fauna, and any conclusion based on such narrow data is certain to be misleading. Of the 71 identical species admitted in our list, several (_e.g._, _Mola_, _Thunnus_) are pelagic fishes common to most warm seas. Still others (_e.g._, _Trachurus_, _Carangus_, _Diodon_ sp.) are cosmopolitan in the tropical waters. Most of the others (_e.g._, _Gobius_, _Gerres_, _Centropomus_, _Galeichthys_ sp., etc.) often ascend the rivers of the tropics, and we may account for their diffusion, perhaps, as we account for the dispersion of fresh-water fishes on the Isthmus, on the supposition that they may have crossed from marsh to marsh at some time in the rainy season. In very few cases are representatives of any species from opposite sides of the Isthmus exactly alike in all respects. These differences in some cases seem worthy of specific value, giving us "representative species" on the two sides. In other cases the distinctions are very trivial, but in most cases they are appreciable, especially in fresh specimens. Further, I expressed the belief that "fuller investigation will not increase the proportion of common species. If it does not, the two faunas show no greater resemblance than the similarity of physical conditions on the two sides would lead us to expect." This similarity causes the same types of fishes to persist on either side of the Isthmus while through isolation or otherwise these have become different as species.