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 enu- 

 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. 

 Boanoke : Carnpostoma ceases here. 

 James : Micropterus and Amhloplites cease. 

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



here. 

 Susquehanna : Ceraiiehthys, Uxoglossum, Chrosomus, Carpiodes, cease. 

 Delaware : Clinostomus, Hypsilepis analostanus, Enneacantlmis, and Lepi- 



dosteus cease. 

 Hudson : ^Semo^i^ws corporai^s, according toF. W.Putnam (verb, commn.), 



ceases. 

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

 trict (IV) are first, then, Salmo, Esox, Anguilla, Perca ; and, secondly, the 

 general types Boleosoma. Semotihis, Sypsilepis, Stilbe, Hybopsis {hifre- 

 natus), Fundulus, and Amiurus ; and the Lake types Lota and Coregomis 



VII. — THE CENTRAL REGION. 



YIP. Species peculiar to the Central region — 12 : 



Anura. 



Spea bombifrons. 



Ophidia. 



Ophibolus multiatratus. 

 Eutaenia radix. 

 Eutaenia vagrans vagrans. 

 Eutaenia sirtalis parietalis. 



Lacertilia. 

 Eumeces septentrionalis. 

 Eumeces inoruatus. 

 Eumeces multivirgatus. 

 Holbrookia maculata maculata. 

 Phrynosoma douglassii douglassii. 



