BLLL. ;!U] 



SHELL-HEAPS 



543 



levels have become consolidated, and that 

 bones embedded with them have lost their 

 organic matter (Wyman), comlitions in- 

 dicative of very considerable age. Great 

 age is also suggested by changes in the 

 river courses, the erosion of bluffs, and 

 the formation of swamps since tiie period 

 of the midden accumulation, as well as by 

 changes in the character of the shells 

 themselves. Dr I'ilsbry, discussing the 

 bearing of the observed faunal changes on 

 the question of antiquity, states that there 

 was a marked change in the characteris- 

 tics of the shells during the period of for- 

 mation of certain of the shell-lields. At 

 the lower levels in the Juniper cr. mounds, 



Mr Moore states that In the shell- 

 mounds he has observed no evidence of a 

 succession of distinct peoples or widely 

 variant cultures; that certain of the great 

 mounds contain no pottery whatever; 

 that in otJiers jiottery-making came iti 

 during the period of their accumulation, 

 while in still others earthenware is dis- 

 tributed in somewhat varying forms with 

 the different layers from base to summit. 

 There is, he believes, satisfactory evidence 

 of progress in culture, and, withal, evi- 

 dence of great age, not, however, of a 

 nature to lead to the belief that the 

 occupancy of Florida extended to a pre- 

 vious geological period. As a result of 



THE Bluff Face 



for example, a dominant species of the 

 shells used is the normal ]'ii:ipara geor- 

 giana. Near the surface a divergent form 

 (altior) appears and prevails. At another 

 point a variety known as limnothauma 

 appears, the most strongly characterized 

 individuals being at or near the surface. 

 " We have no definite standards whereby 

 to measure the time required for the evo- 

 lution of new species or varieties and their 

 establishment as dominant local forms; 

 but judging by the amount of change in 

 the mollusca since the de])Osition of such 

 post-Glacial deposits as the Loess, we can 

 not escape the conclusion that a long pe- 

 riod is indicated." — H. A. Pilsbry, in a 

 letter addressed to Clarence B. Moore, in 

 response to inquiries. 



the investigations of Wyman and Moore 

 an estimate of a thousand years may 

 safely be given as a minimum for the 

 occupancy of Florida by the aborigines. 



The shell-heaps of the rivers flowing 

 into the Gulf on the x., and those of the 

 eastern tributaries of the Mississippi, are 

 numerous and extensive. They are com- 

 posed of the local fresh- water shells, 

 especially the mussels (Unio) and snails 

 (Paludina), and contain characteristic art 

 remains of the region, and in very many 

 cases the osseous remains of the vertebrate 

 animals utilized for food. On the Ten- 

 nessee and Cumberland rs., especially 

 in their middle courses, are extensive 

 deposits that reach a depth of 10 ft or 

 more. They have not been adequately 



