THE NAUTILUS. G9 



The last specimen was bored by a mollusk and, of course, died 

 before spawning. As soon as I removed a small portion of sand the 

 little fellows came pouring out by the hundred, so that I have du- 

 plicated the most interesting find of my life. 



NEW SOUTHEKN UNIOS. 



BY BERLIN H. WRIGHT. 



Unio unicostauis, *p. nov. 



Shell thin, obovate, somewhat inflated, inequilateral. Smooth, 

 with distant and inconspicuous growth lines; epidermis olivaceous 

 with numerous, well separated, indistinct, broad green rays through- 

 out the entire disk, but which are usually most distinct on the pos- 

 terior half: dorsal margin short and straight, anterior margin very 

 short and abruptly rounded, base sub-emarginate, posterior margin 

 rounded and usually (in the male) biangulated; umbos prominent, 

 beaks eroded, umbonal angle obsolete; posterior area with a single 

 little rib extending from beak to the superior posterior margin; beak 

 cavities well defined; dorsal cicatrices deep and close up under the 

 beaks, anterior cicatrices distinct; posterior ones confluent and all 

 smooth; lateral teeth slender, straight and prominent; cardinals 

 lamellate, oblique and prominent ; nacre pale flesh color, pink or 

 red. Width 1|, length 1, diameter § inches. 



Habitat : Spring Creek, Decatur Co., Ga. 



Type in National Museum. 



Remarks : Affinity, U. lienosus. A large lot of these shells has 

 been in hand for two years — and some have been distributed to con- 

 tributors to the collecting fund under the name of U. nigrinus Lea, 

 and U. lienosus Con. var. Its outline is much more obovate than 

 either species and it is smaller and thinner than the latter. The 

 female shells of unicostatus show a still further departure from both 

 of the above-named species in developing a far greater degree of ex- 

 pansion on the base. The little rib on the posterior area is also a 

 distinguishing feature, though it is sometimes nearly obsolete. Its 

 epidermis is never black like that of U. nigrinus. 



