g2 THE NAUTILUS. 



Pisidium. Perhaps half a dozen undetermined species of Pisidium 

 were found in some abundance in the lake and in Sandy Stream. 



Musculium secure (Prime). Common in pools on " the Intervale." 



Campeloma decisum (Say). Winnecook Lake. Common. 



Valvata tricarinata (Say). Winnecook Lake. Common. 



Valvata tricarinata confusa Walk. Winnecook Lake, one spec. 



Amnicola limosa porata (Say). Winnecook Lake and Sandy 

 Stream. By far the most abundant species. 



Lymn^a obrussa (Say). Winnecook Lake. Not found in Aug.- 

 Sept., 1909, but common in Apr., 1910. 



Lymnaa humilis modicelle (Say). Winnecook Lake. Sept., 



1909, rare. 



Lymnsea palustris (Miill). Pools on Intervale, Apr., 1910, com- 



mon. 



Lymn^a decollata (Mighels). Abundant in Lake Winnecook, the 

 type locality (especially late in the season), where it was originally 

 collected by Dr. Milliken. 



Planorbis bicarinatus Say. Winnecook Lake. One specimen, 



Aug., 1909. 



Planorbis campanulatus Say. Winnecook Lake. Not rare in 



Sept., 1909. 



Planorbis exacutus Say. Winnecook Lake. Two specimens. 



Planorbis hirsutus Gld. Common in the lake. 



Planorbis parvus Say. With the preceding. 



Planorbis parvus elevatus (Adams). Several specimens of a 

 minute Planorbis were found in a bit of swamp bordering the lake. 

 All seemed referable to this form rather than to typical parvus. 



Dr. Milliken found also P. trivolvis apparently in some numbers/ 

 but I did not encounter it. 



Segmentina armigera (Say). 



Physa heterostropha (Say). Found in Bacon's Brook and in tht 

 lake in late summer, 1909. 



Physa ancillaria Say. Not encountered until April, 1910, 

 when it was abundant along the shore of the lake, apparently dis- 

 placing the preceding species. 



Aplexa hypnorum (Linn.). Common in pools on the Intervale. 



Carychium exiguum (Say). Windermere. Common, Sept., 1909. 



Cochlicopa lubrica (Miill.). Common around wood piles, 1905, 

 1909. 



1 Mighels: P. trivolviz i+ P. hniusl], Bost. Jour. Nat. Hist., 1843, p. 335. 



