Unionid Mollusks 
87 
pollution exert negative influences over the resident species. For exam- 
ple, two impoundments, Falls Lake on the Neuse near Raleigh and B. 
Everett Jordan Lake on the Haw, have been constructed since the most 
recent samplings in their areas, and a dam creating Randleman Lake on 
the Deep River in Randolph County may soon be built. Clarke (1983) 
found a diverse fauna in the Little River tributary of the Neuse River in 
Wake and Johnston counties, but except for E. complanata, the natural 
molluscan fauna of the Neuse itself had been eliminated, apparently by 
pollution, from Raleigh to Jenny Lind in Lenoir County, a distance of 
more than 136 river km. Similarly, the coastal Trent River tributary 
below Trenton was devoid of mollusks, again probably the result of 
pollution. The situation in the Roanoke system was similar. Clarke 
(1983) found a few empty valves of Anodonta implicata Say and Lamp- 
silis ochracea (Say) in rapids between Lake Gaston dam and Weldon, 
only a few kilometers downstream, but from there to the river mouth no 
unionids were seen. In contrast, the coastal Cashie River tributary con- 
tained living E. complanata and Ligumia nasuta (Say). Clarke attrib- 
uted the depauperate Roanoke River fauna to siltation complicated by 
pollution and fluctuating water releases from Lake Gaston dam. Thus, 
in contrast to the adjacent Neuse and Roanoke Rivers, coastal reaches 
of the Tar River still support a diverse unionid fauna, which includes 
the nationally endangered endemic species Elliptio ( Canthyria ) stein- 
stansana. Every effort should therefore be made to maintain current 
water quality levels in the Tar River, for much of North Carolina’s 
diverse coastal unionid fauna is in imminent danger of disappearing. 
The faunas of the three drainages are compared in Table 1. The Tar 
and Neuse have the same number of species, but the Cape Fear has 50% 
more. Discounting the presence of U. tetralasmus, since malacologists 
disagree on its concept, 10 species are common to all three basins. The 
Tar shares or shared Anodonta imbecilis with the Cape Fear and Alas- 
midonta heterodon with the Neuse, and the Neuse and Cape Fear share 
Anodonta cataracta and perhaps Uniomerus tetralasmus. Lampsilis 
ochracea and Elliptio steinstansana occur only in the Tar, and eight 
species occur solely in the Cape Fear, four of which represent literature 
records from the lower basin. In contrast, no species are recorded solely 
from the Neuse, a possible reflection of its intermediate geographical 
position. The greater fauna of the Cape Fear is partly the result of 
southern elements (V. vibex, A. couperiana, E. icterina, and E. conga- 
raea) that occur northward to this or the proximal White Oak drainage. 
Investigations are now needed in the latter and such drainages as the 
New (Atlantic) and Newport, where no one has looked for unionids. 
Likewise, areas in many watersheds have been sampled incompletely 
and/or insufficiently. Additional undescribed species may well occur in 
the river basins of North Carolina, and resolution of the perplexing 
taxonomic enigmas can come only with additional and intensive empha- 
sis here and in other Southeastern States. 
