THE NAUTILUS. 



also grows with these, but does not live in the mud, but escapes this 

 by growing in the fissures of the cypress trees, a prisoner for life, by 

 choice. 



Thus far my researches have been productive of one new species, 

 U.friersoni Wright, and the extending of habitat of three shells. 

 But I hope to accomplish much more in the future, which, if suc- 

 cessful, will be given to the readers of THE NAUTILUS. 



Frierson Mill, DeSoto Parrish, Louisiana. 



CONTRIBUTION TO A KNOWLEDGE OF UNITED STATES UNIONIDJE. 



BY S. HART WRIGHT. 



( Concluded.*) 

 Unio Swordianus sp. nov. 



Shell oval, massive, very inequilateral, rounded before, highly 

 arched above and rounded at base, very bluntly pointed behind. 

 Sides flattish, constricted slightly or not at all, and the umbonal 

 ridge usually obsolete. Epidermis brownish or somewhat horn- 

 colored, rayless, and the surface roughened with close growth-lines. 

 Ligament darkened, heavy, short and much elevated. Beaks 

 pointed, small and very low. Beak cavity shallow, extending 

 slightly under both cardinal and lateral teeth, thus making it very 

 broad and with obtusely rounded sides. Cardinal teeth double in 

 the left valve, single in the right and smoothish, or crested and 

 short. Lateral teeth heavy, slightly curved, wide apart, arising 

 from a thick dorsal plate. The cardinal of right valve with an ob- 

 long groove at its base. Cicatrices distinct ; dorsal cicatrices con- 

 fluent into an oblong groove under the dorsum. Pallial impression 

 deep and denticulate. Nacre usually pure white, often more or less 

 with waxy discolorations or mottlings or even dirty white. Width 

 4 inches, length 2, diameter 1|. 



Habitat : Powell's Creek, Lee Co., Va. 



Remarks : Affinity, U. bursapastoris B. H. Wright and U. abacus 

 Hald. Our shell differs from the first in having a lighter epider- 

 mis, an arched dorsum, shell cavity greater, beak cavity very much 

 less, being nearly extinct, and the posterior dorsal area narrower 

 and very abrupt in its descent. From U. abacus it differs in the 

 beak cavity, and is much more inequilateral. Ten specimens were 

 obtained from the collector, Mr. T. F. Sword, for whom it is named. 



