206 CALIFORNIA ACADEMY OF SCIENCES 



oceans, our Panama list contains 43, as shown on the appended 'table of distribution. 

 To these should be added the following forms, unrecorded as yet from Panama, but 

 known from other localities on the Pacific Coast of North America: 



Manta birostris • Scomber colias 



Trachurus picturatus Remora albescens 



Trachurus trachurus Mola mola 

 Caranx lugubris Diodon hystrix 



Thunnus thynnus Lampris luna 



Germo alalunga 



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

 now separated by the Isthmus is therefore 54, as coraiiared with the 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, 

 Cirrhitidse and NematistiidiTe) 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 Centropomidse and Dactyloscopidfe are pecu- 

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



Table of Distribution. 



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

 they 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 5), 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 tons principally through the list jiublished 

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

 characteristically South American forms extend their range northward to Panama; 

 and very few species from the Indo-Pacific 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). 



