590 ORTMANN— NAYADES OF 



except that it has salmon-colored nacre ; to my knowledge, this color 

 of the nacre is extremely rare. 



Farther down the Tennessee, at the mussel shoals in Alabama, 

 this species is abundant (Conrad, Hinkley, and Carn. Mus.). 



Type locality: Ohio River and Kentucky River (the type is from 

 Kentucky River, according to Vanatta). 



84. Truncilla torulosa gubernaculum (Reeve), 1865. 

 Unio gubcrnaculitm Reeve, Conch, icon. 16. Unio. '65, pi. 28, f. 146. 



Reeve's figure undoubtedly is this form. Simpson ('14, p. 26) 

 makes this a synonym of the var. rangiana (Lea), and it surely is 

 the parallel form to rangiana of the upper Ohio drainage. It differs, 

 however, distinctly by the dark green color of the posterior expan- 

 sion of the female shell. 



From the typical torulosa, this variety differs by the poorly de- 

 veloped or wanting kno'bs, and by the rather more compressed shell. 



This is the headwaters form of torulosa, and begins to take its 

 place in the region of Knoxville. I have it from the Nolichucky, 

 Chunn's Shoals, Ham'blen Co. ; here, as also in the lower Holston, 

 faint knobs may yet be present. Farther up, the shell is entirely 

 smooth. In the Holston, it goes up to the South Fork at Pactolus, 

 Sullivan Co., Tenn., and to the North Fork at Holston Bridge, Scott 

 Co., Va. In the Clinch, it goes to Dungannon, Scott Co., Va. It is 

 also in the Powell, up to Shawanee, Claiborne Co., Tenn. Locally, 

 it may be quite abundant. 



Type locality: ? 



85. Truncilla turgidula (Lea), 1858. 



Unio tnrgidnlus Lea, '58 (male). — Unio dcviatits Reeve, '64 (fe- 

 male). — Truncilla deviata Walker, 'loh, pp. 77, 78, 81. — Truncilla 

 deviata Simpson, '14, p. 31. 

 Unio tnrgidnlus has been regarded as the male of the female U. 



florentimis, but it belongs to the female deviatns. In Walker's key 



{loh), this has been indicated by the grouping, but it has not been 



expressly mentinoned. 



T. turgidula stands nearest to T. bicmarginata (Lea), a species 



