106 | Trans. Acad. Scr. of St. Louis. 
failed to discover any trace of implements or of wrought 
flints on the surface of the barrens. The most obvious 
and natural explanation would be that the knolls are 
merely the result of surface erosion, remnants of the soil 
mantle that once covered the entire area; but when seen 
in the field this hypothesis can scarcely be entertained 
as a satisfactory one, in view of the peculiar appearance 
of the mounds, as mentioned above. Rejecting these ex- 
planations as unsatisfactory, a third possible one sug- 
gests itself: May not these low mounds have been con- 
structed by some animal long since extinct, that once 
found a congenial habitat in the rocky barrens along the 
banks of these clear, swift flowing streams? However 
their origin may be accounted for, their frequency and 
uniform size render them a singular and striking feature 
of the region. 
The range of most of the peculiar species of plants is, 
as has been stated, co-extensive with the chert outcrop; 
and.it is a curious fact that nearly all of those found at 
the Shoal Creek localities should reappear with the out- 
cropping of the Grand Falls chert north of Turkey 
Creek. Although only about six miles distant this area 
is entirely isolated from the main outcrops, and no trace 
of most of the barrens plants can be found in the inter- 
vening or surrounding country. A few of the species, 
such as Selenia aurea, Cyperus inflexus, Specularia lepto- 
carpa, Portulaca pilosa, Talinum calycinum and Linaria 
canadensis, are also found occasionally in sandy soil or 
in limestone barrens throughout Jasper and Newton 
Counties. 
The occurrence in the barrens of a number of plants of 
such restricted range suggests interesting questions in 
regard to the survival and distribution of species. The 
soil of the uplands in this part of the State is entirely 
residual, resulting directly from the disintegration of the 
underlying rocks. Under such conditions a closer core- 
lation between geological formations and plant distri- 
bution could naturally be expected, although of course, as 
