372 LAND AND FRESH-AVATER SHELLS OF N, A. [PART IV. 



22. S. demissum, Anthony. 



Gyrotoma demissa, Anthony, Proc. Acad. Nat. Sci., p. G4, Feb., 1860. Binnet, 



Check List, No. 31G. BitOT, List, p. 27. 

 Melatonin demissum, Anthony, Reeve, Monog., sp. 9. 

 Schizostoma Hartmanii, Lea, Proc. Acad. Nat. Sci., p. 187, May, 1860. Jour. Acad. 



Nat. Sci., V, pt. 3, t. 35, f. 51. Obs., ix, p. 69. 

 Gyrotoma Hartmanii, Lea, Binney, Check List, No. 322, BuOT, List, p. 27. 



Description. — Shell short, robust, thick, truncate, of a dark horn- 

 color; spire flat by truncation, exhibiting traces of about four 

 ■whorls ; body- whorl cylindrical ; fissure broad, waved and rather 

 deep ; aperture elliptical, within whitish ; columella thickened along 

 its whole extent, but most so at the fissure. 

 My cabinet. 



Length of shell, ten-sixteenths ; breadth of shell, seven-sixteenths 

 of an inch. Length of aperture, seven-sixteenths; breadth of aper- 

 ture, four-sixteenths. 



Observations. — A fine, cylindrical species, whose chief character- 

 Fiff 702 ^s^i<^s ^^^ its very smooth, polished surface, plain russet 

 color and flat, truncate spire; the lines of growth are 

 unusually strong in this species, and the darker lines 

 indicating the terminus of previous mouths are very dis- 

 tinct and numerous, evidencing frequent and many pauses 

 in its growth ; the columella is much bent near its base^^ 

 and a narrow, but distinct sinus is formed at about the middle space 

 between the outer lip and columella. A single specimen only is 

 before me, but seems so very distinct from all others that I have 

 no hesitation in considering it new. — Anthony. 



Mr. Lea considers that this species == his S. constrictum. 

 They are nearly allied, but constrictum is a more elongated, 

 narrower shell, and a comparison of Mr. Anthony's types, 

 kindly placed in my hands by that gentleman, has induced 

 me to believe that constrictum should rather be united to 

 S. rectum.^ Anthony. 



The following is Mr. Lea's description of 



Schizostoma Hartmanii. — Shell smooth, subcylindrical, thick, yel- 

 lowish horn-color, imperforate ; spire raised ; sutures very much 

 impressed ; whorls flattened, the last rather large ; fissure straight 

 and ratlier short; aperture rather small, ovate, white within, obtusely 



