[52 ] 



HELICODISCUS, Morse. . 

 1. Helicodiscus lineata, Say. 



Plate 4, figure 60. 



Discoidal, greenish-yellow; whorls 4, visible below as well 

 as above, with numerous parallel revolving lines, suture well 

 impressed; aperture narrow-lunate; base shallow-concave; a 

 pair of teeth within the outer lip, remote from the margin, 

 and another pair further within and visible through the trans- 

 lucent periphery, in each pair one being placed above, the 

 other below it. 



Diam. 3 mill. 



Maine to Virginia, westwards to Ohio, Texas. 



PSBUDOHYALINA, Morse. 



* Diavfii. = 5 mill. 



1. Pseudohyalina limatula, Ward. 



Plate 4, figure 65. 



Almost planorboid; whorls 4 J, increasing regularly, well 

 rounded; suture very distinctly impressed ; aperture small, al- 

 most round ; umbilicus rather large, as wide as the last whorl, 

 well defined and deep. Color very light, nearly white. 



Diam. 5 mill. 



New York, Ohio, Indiana, Michigan. 



■"■* Diam. = 2| mill. 



2. Pseudohyalina minuscula, Binney. 



Plate 4, figure 63. 



"Whorls 4, depressed, whitish, slowly increasing in diameter; 

 suture deep; aperture sub-rotund; umbilicus large and deep. 



Diam. 2,— 2| mill. 



United States east of Eocky Mountains, from Maine to 

 Florida, and West Indies. 



