HYALINA. 



29 



HYALIIVA, (F£r.) Gray. 



Animal as in Helix. 



Shell generally urabilicated, thin, shining, greenish or reddish 

 horn-color; whirls 5-7, regularly increasing, the last not descend- 

 ing, generally anteriorly dilated; spire depressed, very rarely 

 orbicularly-conic; aperture roundly-lunate; peri- 

 stome thin, acute, straight. 



Jaw simple (neither furrowed nor dentate), arcu- 

 ate, its lower edge acute, with a rostriform projection 

 in the middle. 



Lingual membrane with central tricuspid teeth, a few bicuspid 

 laterals in a straight row, and numerous thorn-shaped, curved 



Fig. 28. 



Fig. 27. 



Liugual dentition of Hyalina viridula. 



uucini in a curving transverse series, modified greatly in size as 

 they pass off laterally. 



StTBGENCs HYALINA, s. str. 



Shell umbilicated, sometimes perforated, depressed, glassy, 

 shining ; whirls 5-6, regularly increasing ; spire very rarely 

 elevated-conic ; aperture roundly lunate ; peri- 

 stome thin, acute, straight. 



Animal with long, slender eye-peduncles 

 and short tentacles ; orifice of respiration on 



Animal of B. cellaria. 



the right side under the edge of peristome ; 

 orifice of generation on the right side of the head. 



Fig. 29. 



