THE NAUTILUS. 

 NEW PISIDIA FROM ALABAMA. 



BT V. STERKI. 



Among the latest sending of Sphczriidse from Alabama and Ten- 

 nessee, collected by Mr. H. H. Smith and sent for examination by 

 Mr. Bryant Walker, there were three Pisidia which could not be 

 referred to any of the established species and not to each other. 

 The mussels are all rather small, and none shows very salient feat- 

 ures, but sufficient to be distinct. The type lots are in the collection 

 of Mr. Walker, and specimens of the same in the Carnegie Museum, 

 Pittsburgh, Pa. (The numbers cited are those of my special collec- 

 tion of Sphceriidce). 



P. albidutn, n. sp. Mussel rather well and regularly inflated, ob- 

 long-rounded on the posterior margin, subtruncate, supero-anterior 

 slope slightly marked ; beaks barely behind the middle, little elevated, 

 rather small and somewhat mamillar, rounded or slightly flattened 

 on top ; surface dull, with fine to very fine, somewhat sharp, irregu- 

 lar, crowded stria?, smooth over the beaks ; color whitish to pale 

 corneous with narrow straw-colored zones along the margins ; shell 

 opaque to subtranslucent, thin ; hinge rather slight, cardinal teeth 

 well formed : the right curved to somewhat angular, slightly thicker 

 at the posterior end, left anterior angular, posterior oblique, slightly 

 curved ; ligament rather slight and short. 



Long. 3.8, alt. 3.2, diam. 2.2 mill. 



Long. 2.8, alt. 2.4, diam. 2 mill. 



Hab. : A spring, Sparta Branch (Murder Creek drainage), 5 miles 

 south of Evergreen, Ala. (Conecuh Co.). [No. 6739]. 



Most specimens in the lot were juv. to half-grown, and only few 

 apparently mature, yet of rather different sizes, as indicated. The 

 oblong outlines, dull surface with rather sharp strias, and the whitish 

 color are sufficient to distinguish this Pisidium. 



P. dispar, n. sp. Mussel short-oval to subquadrate, medium in- 

 flated with the lower part somewhat flattened ; beaks barely or 

 not behind the middle, rather small, moderately prominent ; su- 

 perior margin somewhat curved, bounded by a rounded angle behind, 

 barely any in front ; surface dullish waxy, striae very fine and slight, 

 shallow, crowded, subregular ; color pale-grayish horn, with narrow 

 straw-colored marginal zones ; hinge rather slight, cardinal teeth 

 small, the right curved, with its posterior part thicker; a deep tri- 



