88 



those emptying into the Gulf of Mexico toward the east and northeast, 

 until we reach the rivers of Massachusetts and Maine, where the great- 

 est modification of the fauna exists. The latter fact has been pointed 

 out by Agassiz, who calls this region a "zoological island," and euu 

 merates the characteristic Nearctic genera which are wanting there. I 

 give now a list showing the points at which Mississippi genera cease, as 

 we follow the rivers of the Gulf and Atlantic coasts, so far as our 

 present knowledge extends. 

 Gulf rivers : Haploidonotus has not yet been indicated from eastward 



of these, except in the Lake area. 

 Roanoke : Campostoma ceases here. 

 James : Micropterus and Amhloplites cease. 

 Potomac : Pomoxys, according to Professor Baird (verb, commn.), ceases 



here. 

 Susquehanna : Ceratiehthys, Exoglossum, Chrosomus, Carpiodes, cease. 

 Delaware : Clinostomus, Hypsilepu analostanus, Enneacanthus^ and Lepi- 



dosteus cease. 

 Hudson : Semotihis corporalis, according toF. W.Putnam (verb, commn.), 



ceases. 

 The types remaining in the Atlantic waters of the New England dis- 

 trict (IV) are first, then, Salnio, Esox, Angmlla, Perca ; and, secondly, the 

 general types Boleosoma. Semotilus, HypsUepis^ Stilbe, Hybopsis {hi/re 

 notufi), Fiindulus, and Amiurus ; and the Lake types Lota and Coregoiins 



VII. — THE CENTRAL REGION. 



VIP. Species peculiar to the Central region — 12 : 



Anura. 



Spea bombifrous. 



Ophidia. 



Ophibolus multiatratus. 

 Eutaenia radix. 

 Eutaeuia vagrans vagraus. 

 Eutaenia sirtalis parietalis. 



Lacertilia. 

 Eumeces septeutrionalis. 

 Eumeces inornatus. 

 Eumeces multivirgatus. 

 Holbrookia maculata maculata. 

 Phryiiosonia douglassii douglassii. 



