L. stagnalis var. jugularis (Say) Walk. 

 Body whorl more or less shouldered ; peristome with brown 

 band within. L. emarginata var. angulata (Sowerb.) 

 2 — Bodywhorl narrower, spire more exserted. 



* — Length usually less than 2.5 times the width; length (height) 

 of whorls distinctly less than width. 



L. palustris (Muell.) Sowb. 

 **-Length usually more than 2.5 times the width; length of 

 vvhorls equal to or greater than width. 

 Whorls quite distinctly rounded, suture deep. 



Shell tapering upward gradually and regularly; sur- 

 face usually malleated. L. elodes Say. 

 Shell with two basal whorls relatively much longer; 

 surface rarely malleated. L. reflexa Say. 

 Whorls somewhat flattened, suture not deep. 



Slightly umbilicated ; aperture with a distinct twist, 



L. Jcirtlandiana Lea. 

 Umbilicus closed; aperture long and narrow, with- 

 out twist ; whorls much flattened, short. L. exilis Lea. 

 b — Somewhat less than 20 mm. in length; bodywhorl much enlarged. 



1 — Thin, with short spire and larger bodywhorl (like Succinea). 



Spire conic, bodywhorl convex, columella not distinctly ex- 

 cavated. L. columella Say. 



Spire compressed — acuminate; bodywhorl flattened; colum- 

 ella excavated. L. columella var. clialybea (G-ld.) Mighl. 



2 — Rather heavy; body whorl shouldered; aperture with brown 



band within. L. emarginata var. angulata (Sowb.) 



c — Less than 17 mm. long; body whorl gradually enlarged; shell elon- 

 gated conical. 



1 — Usually brown or brownish; with fine revolving striae; 12 to 



15 mm. long. L. caper ata Say. 



2 — Usually more transparent, and light in color ; no revolving striae. 

 * — Length more than 10 mm. 



Whorls 5.5; very pale horn colored; spire longer than 



aperture; about 12 mm. long, L. pallida Adams. 



Whorls 5; yellowish; aperture usually about equal to 



spire; about 15 to 17 mm, long, L. obrussa Say. 



**-Length less than 10 mm. 



Whorls 6; length. 8 to 9 mm.; umbilicus distinct; shell 



reddish or yellowish white. L. modicella (Say) Jay, 

 Whorls about 5; length 3 to 7 mm.; umbilicus small or 



closed. 



Shell usually more than 4 mm. long; whorls not 

 shouldered. L. parva Lea. 



Shell usually less than 4 mm. long; whorls somewhat 

 shouldered. L. dalli Baker. 



19. — -Aplexa hypnorum (L.) Chem, 



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