304 PROCf^.EDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



America, 18G9, 397). Dr. Gilnther assumes that nearly one-third of the 

 total number of species of marine fishes on the two shores of tropical 

 America will be found to be identical. Hence he infers that there must 

 have been, at a comparatively recent date, a depression of the isthmus, 

 producing an intermingling of the tsvo faunjie. 



This discrepancy arises from the comparatively limited representa- 

 tion of the two faunae at the disposal of Dr. Giinther. He enumerates 

 19o 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 assump- 

 tion of complete identity as erroneous, so that taliing 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 conclusions based on 

 such narrow data are certain to be misleading. 



Of the 71 identical species admitted in our list, several (e. </., Mola, Or- 

 cynus) are pelagic fishes common to most warm seas. Still others (c. ^., 

 Trachurus, Caranx^ Diodon, sp.) are almost cosmopolitan in the tropical 

 waters. Most of the others {e. </., Gobins, Gerres, Centropomus, Ga- 

 leichthys sp., &c.) often ascend the rivers of the tropics, and we may 

 account for their ditfusion jjerhaps, 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 difi"erences 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 on fresh speci- 

 mens. 



I am therefore brought to the conclusion that the fish faunae of the 

 two shores of Central America are substantially distinct, so far as species 

 are concerned, and that the resemblance between them is not so great as 

 to necessitate the hypothesis of the recent existence of a channel across 

 the isthmus, j^ermitting the fishes to pass from one side to the other. 



Indiana University, J»?j/ 18, 1885. 



NOTE ON SOME LINNiEAN NAMES OF AMERICAN FISHES. 

 By DAVID !><. JORDAN. 



In the current volume of these Proceedings (pj). 193-208) is a very 

 useful "contribution to the stability of American ichthyological no- 

 menclature," entitled "On the Americnn Fishes in the Linnaean Collec- 

 tion," by Messrs. Goode and Bean. 



Most of the changes suggested in this pai)er are well founded, and 

 some of them have already been adopted by the writer from verbal 

 statements of Dr. Bean, A few seem to need further discussion. 



