THE NAUTILUS. 17 



gical literature. In 1897 I collected a few hours in Oklahoma City, 

 obtaining the following species : 



Polygyra texasiana (Moric). Planorbis bicarinatus (Say). 



Polygyra monodon (Rack.). Planorbis parvus (Say). 



Helicodiscus lineatus (Say). Physa sp. 



Zonitoides minuscula (Binn.). Lampsilis anodontoides (Lea). 



Zonitoides arborea (Say). Lampsilis purpuratus (Lam.). 



Zonitoides nitida (Miill.). Lampsilis gracilis (Bar.). 



Euconulus fulvus (Miill.). Lampsilis parvus (Lea). 



Strobilops amnis (Pils.). Quadrula lachrymosa (Lea). 



Pupoides marginatus (Say). Quadrula pustulosus (Lea). 



Bifidaria armigera (Say). Tritogonia tuberculata (Bar.). 



Bifidaria contracts (Say). Symphynota complanata (Bar.). 

 Lymnfea probably techella(Hald.). Sphagnum sp. 



Planorbis Irivolvis (Say). Pisidium sp. 



NEW SPECIES OF PISIDIUM. 



BY V. STERKI. 



Pis. minusculum, n. sp. Mussel minute, slightly oblique, medium 

 inflated; superior margin short, moderately curved, bounded by 

 slightly projecting, rounded angles; supero-anterior and posterior 

 slopes little curved or straight, posterior end rounded, anterior a 

 rounded angle situated much below the median longitudinal line, 

 inferior margin rather well curved; beakes slightly posterior, rather 

 large, rounded or somewhat flattened, moderately projecting over 

 the hinge margin; surface with very fine, slight striae, somewhat 

 shining, color pale horn, shell translucent; hinge rather stout, car- 

 dinal teeth: the right strongly curved, its posterior part much 

 thicker and grooved, left anterior rather short, well curved, the 

 posterior longer, oblique, curved; "laterals" strong, the outer ones 

 in the right valve well formed; ligament, short, thick. 



Long. 2.2, alt. 1.8, diam. 1.5 mill. 



Habitat: Fox river, Wisconsin, collected by the late Geo. H. 

 Marston; types in the collection of the University of Wisconsin and 

 that of the Carnegie Museum. 



A number of specimens of this little Pisidium was received in 

 1895 and then recognized as a new species, and again in 1904, when 



