286 ORTMANN—CORRELATION OF SHAPE AND 
intervenes from which no shells are at hand, and that above Offutt 
the Powell flows into the Clinch, the latter thus suddenly decreasing 
in size. 
Material from the Powell is scanty, but it fits into the scheme. 
It is thus clear that also the cuneolus-group is subject to the law. 
It also holds good, as far as my material goes, in the Tennessee and 
its tributaries in northern Alabama, where this type of shells also 
seems to be abundant. 
Group oF FUSCONAIA EDGARIANA IN THE UPPER TENNESSEE-SYSTEM. 
I distinguish the following two forms, but use the specific name 
of edgariana (see F. cor, Ortmann, ’18, pp. 532, 533). 
I. FUSCONAIA EDGARIANA (Lea).—Dia. 50 per cent. or over. 
Unio edgarianus Lea, ’40 (Holston R., Tenn.; Tennessee R., Flor- 
ence, Ala.).—Pleurobema edgarianum Simpson, ’14, p. 741. 
Dia, (ea): 64 per cent; (Simpson) :*58, 60; 76 percent. 
Unio obuncus Lea, ’71 (Tuscumbia, Ala.; Holston R., Tenn.).— 
Synonym to edgarianum, according to Simpson. 
Dias y( ea) 253" per icent. 
Unio andersonensis Lea. ’72 (Holston R.; Clinch R., Anderson Co., 
Tenn.).—Synonym to edgarianum, according to Simpson. 
Diae (Lea) +76 percent; 
2. FUSCONAIA EDGARIANA ANALOGA (Ortmann).—Dia. less than 
50 iper cent: 
Fusconaia cor analoga Ortmann, ’18, p. 533 (Clinch R., Speers 
Ferry ). 
My material from Clinch River has furnished the following 
figures. 
Loc. No. Max. Min. Av. 
Clinch River. 
Edoemoor sacle anche noses I 58 58 58 edgar. 
Needham Hondeeneaeeenee see eee 2 SI 42 46.5 anal. (edgar.) 
GlinchmRivers Stattom sect soccer 2 48 47 47.5 anal. 
Sneedville giweiacis Morass noes I 49 49 49 anal. 
Ghinchimbondie see or acmeoe done: I 42 2 42 anal. 
Speensimbienty?  Viiav aise teractions exe 8 49 43 46 anal. 
Clinch pornties.ttes onto cece tomes 6 45 41 43 anal. 
Seg ENDL. See NAR Ei ee Ae eat 7 45 40 43 anal. 
Gitlin A Rea § Be vey chemeta Drone erature obs 2 48 41 45 anal. 
Glevielandaee eae ncpinne tine eee 6 44 40 42 anal. 
