294 ORTMANN—CORRELATION OF SHAPE AND 
fera) of the lower parts of the river passes gradually into the more 
compressed form (tuberculata) of the headwaters, I have not suffi- 
cient material to substantiate this by measurements, since all my 
material, from the middle Ohio upwards, and from the upper Ten- 
nessee, clearly belongs to the compressed tuberculata-type. But the 
general rule, at least, is thus confirmed, that the swollen form, 
granifera, is not found in the upper course of these rivers. 
Group OF LEXINGTONIA DOLABELLOIDES IN THE UPPER TENNESSEE- 
SYSTEM. 
The dolabelloides-group is common in the upper Tennessee, and 
also in the Tennessee-drainage in Alabama, and I again distinguish 
a swollen and a compressed form, the first in the larger rivers, the 
second in the headwaters. They pass gradually into each other, 
and the line drawn between them, at the diameter of 50 per cent., 
again is artificial. The nomenclature and synonymy is as follows :1° 
I. LEXINGTON DOLABELLOIDES (Lea).—Dia. 50 per cent. or over. 
Unio dolabelloides Lea, ’40 (Holston R., Tenn.) —Pleurobema dol. 
Simpson, 145 ps 752: 
Dia- (ea) 263 per cent.; (Sinipson) .67-and 71 per cent. 
Unio thorntoni Lea, ’57 (Tuscumbia, Ala.) —Recognized as syn- 
onym by Simpson. 
Dial (eat: GOsper cent: 
Unio mooresianus Lea, ’57 (Tuscumbia, Ala.)—Synonym, accord- 
ing to Simpson. 
Dia. (Gea): (607 per cent. . 
Unio recurvatus Lea, ’71 (Tennessee R.; Holston R.).—Synonym, 
according to Simpson. 
Dia (ea) 63 percent: 
Uino circumactus Lea, ’71 (Florence, Ala.; Holston R., Tenn.).— 
Synonym, according to Simpson. 
Dia: (Ikea) 2 58" per cent. 
Unio subglobatus Lea, ’71 (Florence, Ala.; Nashville, Tenn.).— 
Synonym, according to Simpson. 
Dia: (Lea)s-73 percent. 
19 See Ortmann, Proc. Amer. Philos. Soc., 57, 18, pp. 545, 546. 
