STATION IN FRESH-WATER MUSSELS. 299 
GROUP OF PLEUROBEMA OVIFORME IN THE UPPER T7ENESSEE- 
DRAINAGE. 
Great confusion has prevailed hitherto with regard to the shells 
belonging here. In a previous paper I have tried to bring order 
into this group,” and have divided it into three subspecies, because 
21 Pr. Amer. Philos. Soc., 57, 18, p. 550 ff. 
the oldest name given was applied to a form intergrading between 
the extremes. The synonymy is as follows. 
I. PLEUROBEMA OVIFORME (Conrad).—Dia. 40 to 49 per cent. 
of length. . 
Unio oviformis Conrad, ’34 (Tennessee).—Pleurobema oviforme 
Simpson, 14, p. 745. 
Dia. (Simpson) : 43 per cent. 
Unio ravenelianus Lea, ’34 (French Broad R., Asheville, N, Car.) 
—Pleurobema rav. Simpson, *14, p. 796. 
Dias (lea) =, 43 per cent.; (Simpson): 40, and 43 ‘perscent: 
Another specimen measured by the latter has 50 per cent. 
Unio lesleyi Lea, ’60 (Kentucky, Tennessee).—Pleurobema lesl. 
Simpson, ’14, p. 744. 
Dia. (Lea): 43 per cent. Specimens measured by Simpson give 
31 and 39 per cent., and, consequently, do not belong here. 
Unio ornatus Lea, ’61 (Alabama).—Pleurobema orn. Simpson, ’14, 
p. 746. 
Dia. (Lea) : 43 per cent. ; (Simpson, supposed type) : 44 per cent. 
Unio clinchensis Lea, ’67 (Clinch, French Broad, Holston).—Pleu- 
robema clinch. Simpson, ’14, p. 743. 
Dia. (Lea and Simpson) : 44 per cent, 
Unio conasaugaénsis Lea, ’72 (Conasauga Cr., Monroe Co., Tenn.), 
—Pleurobema con. Simpson, ’14, p. 800. 
Dia. (Lea): 45 per cent.; (Simpson) : 40 per cent. 
2. PLEUROBEMA OVIFORME ARGENTEUM (Lea).—Dia, less than 
40 per cent. 
Unio argenteus Lea, ’41 (Holston R., Tenn.).—Pleurobema arg. 
Simpson, 714, p. 798. 
Dias. @eea) 128 per cent.; (Simpson) 32 percent. 
