THE NAUTILUS. 135 



Lampsilis claibornensis Lea. 



" lienosus Con. Not typical ; referrable to Lea's caligino- 



sus. 



" lienosus unicostatus H. B, Wr. 

 " vibex Con. (approaching var. nigrinus Lea.) 

 Anodonta gibbosa Say, 

 Unio singularis B. H. Wr. 



" arctatus tortivus Lea. Very abundant and extremely vari- 

 able. 



" coruscus Gld. 

 " nigellus Lea var.? Very close to some forms of the variable 



arctatus tortivus Lea. 



" curvatus Lea, a single young shell is thus named by Mr. W. 

 A. Marsh Sr. It is quite similar to young specimens of 

 the Moccasin Creek forin referred to obnubilis (nolani) by 

 Mr. Marsh, but differs in being rather more elongated, 

 more pointed and less broadly rounded posteriorly. 

 Unio chipolaensis, n. sp. PI. ix. figs. 6 and 7. 



Shell ovate, not very thick, somewhat inflated in the umbonal 

 region, evenly rounded before and triangulate behind with a slight 

 emargination just above the superior posterior angle ; dorsal margin 

 decidedly curved, basal margin slightly but regularly curved, 

 epidermis smooth, chestnut-colored, darkening to black on the umbos, 

 with several darker lines indicating arrested periods of growth. 

 Umbonal slope well rounded towards the beaks, but flattening out 

 and becoming slightly biangulate posteriorly. Beaks prominent, 

 apparently incurved when perfect. Cardinal teeth compressed, 

 crenulate; those in the left valve are nearly in a straight line. 

 Lateral teeth rather long, slender and slightly curved. Cicatrices 

 distinct. Cavity of the beaks large and rounded. Nacre salmon- 

 color, darker anteriorly. 



Length 32, width 56.5, diam. 22 mm. 

 Chipola River, Fla. 



This species is a member of group of U. buckleyi and is disting- 

 uished by smooth, chestnut epidermis, entirely without rays, but 

 ornamented with concentric dark bands such as occur in Pleurobema 

 chattanoogaensis, inflated umbonal slope, prominent beaks and bian- 

 gulated posterior extremity with a slight emargination above. It is 

 related to some forms of U. burtchianus B. H. Wr, but differs in 



