76 



THE AMERICAN NATURALIST [Vol. XLII 



is that of the fishes on the two sides of the isthmus of 

 Panama. Living under essentially the same conditions, 

 but separated since the end of the Miocene Period by the 

 rise of the isthmus, we find species after species which 

 has been thus split into two. These geminate species, a 

 hundred or more pairs in number, were at first regarded 

 as identical on the two shores of the isthmus. Later one 

 pair after another was split into recognizable species. 

 The latest authority on the subject, Mr. C. T. Regan, 

 seems to doubt if any species of shore fishes are actually 

 identical on the two sides of the isthmus. 



To make this clear, though at the risk of being tedious, 

 I give below a partial list of these geminate species about 

 the isthmus of Panama : 



Clupanodon libertatis 



Centropomus medius 

 Centropomus ensiferus 

 Epitit ■ plains analogus 

 Alphestes multignttatus 

 Dermatolcpis punctatits 

 IFgpoplcrtnis lampritrus 

 Lutianus novrmfdsciatns 



rgentix 



Lutianm 



Lutianus guttatus 

 Hcemulon se.rfaseiatu m 

 Hcemulon scudderi 

 llirm nhm st< iniUichnrri 



Xiishniid cinereum 

 Enrinostomns pseudogula 

 Kyphosus incisor 

 fsr>j)isthi(s parvipimiis 

 Nebris microps 

 I.arimxs fasciatus 



