200 CALIFORNIA ACADEMY OF SCIENCES 



oceans, oiir P«imm« list contains 43, as shown on tho appeiulod 'tuhlo of distrihiition. 

 To these shouKI be aiKloil the followinjj forms, nnrecordeil as yet from Panama, l)ut 

 known from.otlier localities) on the Pacific Coast of North America: 



Manta l>irostris Scomber colias 



Trachuriis picturalus Reinora albescens 



Trachurus trachurus Mola mola 



Caranx lugubris Diodon hystrix 



Tluinnus thyniuis Lampris lima 

 Gcrino alaliinira 



The total number of identical species which we recognize in the two faunas 

 now separated by the Isthmus is therefore 54, as compared with llie 71 enumerated 

 by Jordan (1885). It is obvious, however, that the striking resemblances between the 

 two faunas are shown as well by slightly divergent as by identical species, and the 

 evidence in favor of interoceanic connection is not weakened by an increase in one 

 list at the expense of the other. All evidence concurs in fixing the date of that 

 connection at some time prior to the Pleistocene, probably in the early Miocene. 

 When geological data shall be adequate definitely to determine that date, it will give 

 us the best known measure of the rate of evolution in fishes. 



Of the 82 families of fishes represented at Panama, all but 3 (Cerdalidse, 

 CirrhitidiB and Nematistiid;^) occur also on the Atlantic side of Central America; 

 while of the 218 genera of our Panama list, no fewer than 170 are common to both 

 oceans. The well-developed families Centropomida' and Dactyloscopid;^; are pecu- 

 liar to the two tropical faunas now separated by the Isthmus of Panama. 



Table of Distkibution. 



The following table indicates the distribution of Panama fishes, in .so far as 

 tiiey have been reported from the Gulf of California, the Galapagos Islands, the 

 coasts of Ecuador and Peru, and the Atlantic Ocean. For the Gulf of California, 

 we have depended upon Jordan (1895 i), Evermann and Jenkins (1891), and Gill 

 (1862). For the Galapagos Islands, we have at hand a manuscript list by Messrs. 

 Snodgrass and Heller. Ecuador is known to us principally through the list published 

 by Boulenger (1898-9), and Peru through the paper by Abbott (1899rt). Very few 

 characteristically South American forms extend their range northward to Panama; 

 and very few species from the Indo-Paeific fauna reach the continental shore-line, 

 though a somewhat larger number of the latter find their way to the series of out- 

 lying islands (Revillagigedos and Galapagos). 



