245 



side of VVrightsville, but being on a moving train at the time I 

 was able to recognize only two species there, Talinnm and Sela- 

 ginella acantlionota, both of which were new to Johnson County. 

 I have no doubt, however, that CJioiidropliora virgata and several 

 of the other species above mentioned can be found there also. 



The fact that the Washington County rock areas are within 

 30 miles of the fall-line suggests a route by which some of the 

 rock-loving plants may have entered the coastal plain. At the 

 time of preparing my description of the region I had no definite 

 knowledge of the occurrence of this rock so far inland, and did not 

 allow for it on the map. This must be about its extreme inland limit, 

 however, for along the Central R. R., which crosses the county 

 a few miles farther inland, there seems to be no rock of this kind, 

 nor even any pine-barrens. The locality described is just about 

 on the divide between the Ogeechee and Oconee rivers, so it has 

 not been eroded as much as the country a little east and west of it. 



The topography of this extreme northern edge of the Altamaha 

 Grit region is not exactly typical, and it seems likely that the 

 more homogeneous lower phase of the formation, which is ex- 

 posed along the rivers farther south * and perhaps determines the 

 typical topography which has been described elsewhere,! is want- 

 ing here, allowing the underlying Oligocene or Eocene rocks to 

 approach the surface. More field work is needed for the deter- 

 mination of this point. An interesting and perhaps correlated 

 fact is that this seems to be the only part of the Altamaha Grit 

 region which is outside of the range oi Pimis Elliottii, the inland 

 limit of which passes through Johnson County a iQ.\N miles south- 

 east of Wiightsville. 



Up to the present time I have seen unmistakable outcrops of 

 the Altamaha Grit in the counties of Jenkins, |§ Washington, 

 Johnson, Tattnall, Toombs, % Laurens, § Dodge, Jeff Davis, %% 

 Coffee, Wilcox, Crisp, ^ and Turner, |§ and have been reliably in- 



* See Ann. N. Y. Acad. Sci. 17 : 22. 1906; Torreya 6 : 199. 1906. 



I Bull. Torrey Club 32 : 146. I905 ; Ann. N. Y. Acad. Sci. 17: 23. 1906. 



J These five counties are among those created in 1905 and therefore do not 

 yet appear on most maps. 



\ In these counties I have seen the rocks only from trains and have not been able 

 to make any notes on their vegetation. 



