SCHIZOSTOMA. 



379 



As this shell was one of the first species of the genus 

 described, there did not appear to be so much necessity at 

 that time for an accurate and extended description. 

 That of S. quadratum, by Mr. Anthony, will give 

 a better idea of the specific characters. 



Fig. 711. 



Gyrotoma quadrata. — Shell short, smooth, fusiform, rather 

 thick, olivaceous ; spire short, composed of about four 

 very low whorls, the upper two being partially obliterated by ero- 

 sion ; fissure rather broad, waved, but not remarkably deep ; sutures 

 distinct ; whorls distinctly, but not squarely, shouldered ; aperture 

 elliptical, occupying more than half the length of the shell; within 

 three-banded ; columella with a light callous deposit. 

 Habitat. — Coosa Eiver, Alabama. 



Length of shell, uiue-sixteonths ; breadth of shell, seven-sixteenths 

 of an inch. Length of aperture, six-sixteenths ; breadth of aperture, 

 three-sixteenths of an inch. 



Observations. — The most remarkable characteristic at first view of 

 this species is its short, square form ; its color is dark, and the bands, 

 Fig 712 Fis 713 "v^'hich are very broad, are not very distinct; 

 hence its general aspect is not so pleasing to 

 the eye as many others ; the fissure is broadly 

 separated from the body of the shell ; outer lip 

 very sharp and sinuous, forming, with the colu- 

 mella, a small not very distinct sinus at base. 

 In form it approaches most nearly perhaps to G. salebrosa (nobis), 

 but is more delicate in texture, thinner and has no armature as in 

 that species. — Anthony. 



Mr. Lea considers quadrata, Anthonj^, to be a s^-nonj'me 

 of his S. incisum. An inspection of a number of specimens 

 of both species enables me to agree with him entirely. To 

 these I unite S. virens, Lea, recently published, believing it 

 to be a small variety of the same species. 



Schizostoma virens. — Shell very slightly nodulous, very much in- 

 flated, rather thick, dark green, A'ery minutely striate, imperforate; 

 spire short ; sutures impressed ; whorls rather flattened and with 

 three bands; lip-cut oblique, short; aperture elongate, nearly pear- 

 shaped, within darkly banded; columella whitish and thickened 

 above ; outer lip sharp and sinuous. 



