116 TiIK NAUTIU'S. 



coluraella concave with a heavy, broad, flat callus which extends over 

 the parietal wall, and separated below the axis by a rather wide axial 

 groove. Lip simple but thickened within, especially below. 



Alt. 3^, diam. 3^ mm. 



This species is distinguished from other described species with an 

 axial groove by its small size and sub-globular shape. It is most 

 closely related to S. tennesseensis. but differs in being smaller, more 

 globular ; more solid, smaller aperture, narrower axial groove, and 

 broad, flat columella. S. excavatus, which is about the same size, is 

 too entirely different in shape to be confounded with it. 



SOMATOGYRUS PENNSYLVANicus Walker. PI. 5, figs. 17 and 18. 



In the Spring of 1905, I collected a few specimens of this species 

 under stones at the upper end of Island Park in the Potomac River 

 at Harper's Ferry, Va. The occurrence of this species in a different 

 drainage system is of interest. The shells are rather larger than 

 those of the original lot from Columbia, Pa., and exhibit the two 

 forms noticed in S. virginica and quadrata. The dimensions of the 

 specimens .figured are : 



Fig. 17, alt. 3.75, diam. 2.5 mm. 



Fig. 18, alt. 4, diam. 3 mm. 



PYRGULOPSIS MISSISSIPPIENSIS (Pils.). PI. 5, fig. 15. 



Pyrgula scalariformis mississippiensis Pils., American Naturalist, January, 

 1886, p. 75. 

 Pyrgulopsis mississippiensis Call and Pilsbry, May, 1886. 



One of the most interesting discoveries made by Mr. Hinkley dur- 

 ing his trip was the finding of this species living in great numbers in 

 Shoal Creek near Florence, Ala. This is the first time the species 

 has been found alive ; the original specimens having been all dead 

 shells. We are thus enabled to supply two particulars in which the 

 original description was necessarily defective. The epidermis is of 

 a clear yellowish-horn color and the operculum agrees with the 

 generic diagnosis in being " ovate, thin, corneous, spiral, with the 

 polar point well forward and approximating the columella." The 

 apices of all the mature Shoal Creek specimens were eroded. 



AMNICOLA PILSBRYI, n. sp. PL 5, figs. 11 and 16. 



Shell very small, umbilicate, globose, conic ; light horn-colored, 



