1 78 College of Forestry 



seen on the shore until hite in July, and none were observed in 

 localities where they were abundant in the fall of the previous 

 year. Early spring collecting in the lake is highly desirable. 



Genus PsEUDOsucciNEA Baker 



84. Pseudosuccinea columella (Say). Not collected in 1916. 



85. Pseudosuccinea columella chalybea (Gould j. 

 Collected in but two habitats, a protected bay on Nyrnplicea 



leaves and a partly enclosed lagoon among filamentous alg?e, 

 CEdogonhiiu. At both localities the species was fairly abun- 

 dant. All individuals were immature, however, measuring 

 from S to 13 mm. in length. 



Genus Acella Haldeman 



86. Acella haldemani (' Deshayes ' Binney). 



Observed in two habitats on submerged vegetation, always in 

 a protected situation, in water from one to four feet deep. 



The ecology of this, the slenderest of our Lymnaeas, is but 

 little known for the greater part of the year. It has been found 

 more or less abundantly in the fall but its whereabouts during 

 other parts of the year is a matter of conjecture. Kirkland 

 (Baker, '11, p. 197) believes it to be a deep water species 

 which migrates toward shore to spawn in the fall. Sargent 

 ('96, p. 127) found it only in the fall in Heath Lake, Minne- 

 sota, and says " where do they keep themselves in the summer." 

 Its whereabouts in the summer can now be stated, for several 

 specimens were found in July in Lower South Bay. The indi- 

 viduals were all young, none exceeding 10 mm. in length, and 

 were invariably found on the leaves or stem of the pond-weed, 

 Potamogeton interruptiis. It is evident that they do not retire 

 to deep water, but only to the zone where this pond-weed, or 

 perhaps other suitable vegetation grows, which may be in water 

 from two to six feet deep. The shells are very difficult to 

 find for when living they are nearly the color of the leaf and 

 look much like a young leaf beginning growth. The Potamo- 

 geton is admirably adapted for the use of this snail, its leaves 

 being very long and exceedingly narrow and flat. It is prob- 



