STATION IN FRESH-WATER MUSSELS. ' 299 



Group of Pleurobema oviforme in the Upper Tenessee- 



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. Pliilos. Soc, 57, '18, p. 550 fif. 

 the oldest name given was applied to a form intergrading between 

 the extremes. The synonymy is as follows. 



1. 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. 



Dia. (Lea): 43 per cent.; (Simpson): 40 and 43 per cent. 

 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 ornatns 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 conasaucfaensis 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 org. 

 Simpson, '14, p. 798. 

 Dia. (Lea) : 38 per cent.; (Simpson) : 32 per cent. 



