86 Paul W. Parmalee, Walter E. Klippel, Arthur E. Bogan 



ers such as the Tennessee having a sandy-gravel substrate with rapid 

 currents (Stansbery 1971). Although a few individuals of some of these 

 species (e.g. interrupta, obliquata) may continue to survive after im- 

 poundment (Parmalee et al. 1980), they do not or cannot propagate, 

 and the species within the affected sections of the river eventually die 

 out. Only P. triquetra still occurs in viable populations in upper East 

 Tennessee and locally in the Midwest and Great Lakes states. 



All shells of the 12 species of Plagiola represented in the middens 

 amounted to approximately 8% of the total sample; valves of arcaeform- 

 is, propinqua, and torulosa comprised 6.5% of this total. Two distinct 

 forms of P. torulosa have been recognized (Ortmann 1918): P. t. torul- 

 osa, with the more inflated shell with a radial row of prominent knobs 

 across the middle, occurred from about Knoxville downstream; the 

 form P. t. gubernaculum, with a more compressed shell and poorly devel- 

 oped or wanting knobs, occurred in streams above Knoxville. Although 

 valves of the form torulosa predominate in the Chickamauga Reservoir 

 middens, a few approach the typical upstream form gubernaculum. 



In a recent taxonomic revision of this complex, Johnson (1978) 

 synonymized the species P. lewisi with P. flexuosa, although not all 

 malacologists (e.g. Stansbery 1971) agree with this approach. Valves of 

 these two species, or the species P. flexuosa, occurred only sparingly in 

 the middens, which may reflect the former rarity of P. flexuosa in the 

 Tennessee. Except for arcaeformis, propinqua, and torulosa, the same 

 may be said of the other species of Plagiola. Of interest is the fact that 

 only five valves of P. triquetra, the one species still locally common and 

 widespread in streams of eastern Tennessee and the Great Lakes area, 

 were recovered in the middens. Warren (1975) listed only four valves of 

 this species in a sample of 60,350 valves from the Widows Creek site; 

 Morrison (1942) reported it absent from the Pickwick Basin mounds. 

 This rather ubiquitous inhabitant of numerous smaller streams and 

 tributaries of the Tennessee apparently did not become well established 

 in the shoals and riffles of the main river. This also seems to have been 

 the case with capsaeformis, turgidula, interrupta, and florentina, all spe- 

 cies of small-to-medium size rivers. It is of further interest that all shells 

 of Plagiola spp. comprised 1% of the valves from the Mississippian 

 component sites, but averaged about 6% of the totals from the Middle 

 and Late Woodland sites. 



Fusconaia subrotunda (Lea 1831) occurred in all middens and var- 

 ied from about 3.5% of all valves in the Late Woodland and Mississip- 

 pian sites to 7.5% in the multicomponent Middle/ Late Woodland sites. 

 Pardue (1981) found very few specimens of this mussel in the Chicka- 

 mauga and Watts Bar reservoirs and we doubt that it will ever return to 

 a semblance of its former abundance. Cyclonaias tuber culata (Raf. 

 1820), however, another ubiquitous although slightly less common shell 



