450 W. F. BLAIR 



1939) live about 200 miles farther west. This species is closely asso- 

 ciated with forests throughout its range, and the relicts in Texas 

 and Oklahoma as well as the Mexican relicts must have reached 

 their present locations by way of forests. 



The neotenic salamanders of the genus Eurycea on the Edwards 

 Plateau of Texas appear to be closely related to similarly adapted 

 E. tynerensis of the Ozarks and thus indicate a southward as well as 

 westward shift of conditions favorable for this group. The two groups 

 are separated today by a distance of over 400 miles. In both areas, 

 these salamanders are restricted to cool springs in forested regions. 

 Another plethodontid genus (Plethodon) shows an interesting but 

 more complex pattern of relictual distribution (Fig. 7). A population 

 of P. glutinosus on the Edwards Plateau is disjunct from the main 

 distribution of this eastern species, which reaches into eastern Texas. 

 On the Edwards Plateau this species is found in relatively moist 

 ravines and around springs or entrances to caves. Plethodon ouachitae 

 of Rich Mountain in southwestern Arkansas appears to be a relict 

 of an Appalachian group (Dunn and Heinze, 1933). x'\nother species 

 of this genus (P. neomexicanus) occurs in spruce-fir forests of the 

 Jemez Mountains of northern New Mexico (Stebbins and Riemer, 

 1950). This species is described as "close to Plethodon cinereus of 

 eastern United States and Canada." There are disjunct populations 

 of P. cinereus in the Ozarks and in eastern Missouri, but the main 

 body of the population is east of the Mississippi River. Stebbins 

 and Riemer surmised that southward dispersal through the Rocky 

 Mountains accounted for the New Mexico population, but dispersal 

 directly across Oklahoma in the Wisconsin seems a more plausible 

 explanation. The genus occurs along the Pacific Coast from northern 

 California to British Columbia, and there is a relict species in north- 

 ern Idaho. Another plethodontid genus with wide disjunctions is 

 Amides. One species lives in the Appalachian region of the eastern 

 United States, one in the Sacramento Mountains of southern New 

 Mexico, and three along the Pacific Coast. Lowe (1950) hypothesizes 

 geographical separation of the New Mexico species {A . hardyi) dur- 

 ing early Pliocene. We suggest alternatively that a connection 

 between it and the eastern population could have existed as re- 

 cently as the late Pleistocene. 



An area on the floodplain of the San Marcos River in Gonzales 

 County, Texas, has an assemblage of eastern coastal plain plants 



