op coNcnoLOdY. 251 



ascertained to be one of the few European species common 

 to both continents. It has been known among American 

 couchologists, until recently, as IT. lucida, Drap., which is, 

 however, a synonym of S. nitida, Mull. 



14. Hyalina arborea, Say. 



Plate 3, figure 17. 



Whorls 4|, regularly and moderately increasing, depressed 

 turbinate, thin, amber colored, smooth, shining ; lip slightly 

 flexuose ; umbilicus moderate and deep. 



Diam. 5 — 6 mill. 



Georgia and northwards beyond Canada ; westwards to the 

 Rocky Mountains ; Los Angeios Co., California. 



15. Hyalina electrina, Gould. 



Plate 4, figure 25. 



Whorls 3|, depressed, pale, shining, the last rapidly en- 

 larging towards the mouth ; umbilicus very small, deep ; lip 

 not flexuous. 



Diam. 4 mill. 



Maine to Georgia, and westwards to Iowa. 



Differs from H. arborea in its pale color, more depressed, 

 smaller, fewer whorls, and their more rapid increase, and very 

 narrow umbilicus. 



16. Hyalina ottonis, Pfeiffer. 



Plate 4, figure 26. 



Orbicularly depressed ; whorls 4, very light colored, nearly 

 white, suture narrow, periphery angular ; superior surface of 

 whorls obliquely declining, inferior well rounded ; umbilicus 

 narrow and deep. 



Diam. 5, altitude 2*5 mill. 



Florida and West Indies. 



Much lighter colored and smaller than H. arborea, also 

 angled at the periphery and not so widely umbilicate. 



