TilK NAUTILUS. 103 



Pisidium contorlum Prime. Abundant. 



Pisidium pauperculum Sterki. Rare. 



Pisidium rotundatum Prime. Not common. 



Pisidium scutellatum Sterki (?). Rare. 



Pisidium variabile Pme. Rare. 



Pisidium ventricosum Pme. Common. 



Pisidium walkeri var. mainense Sterki. Rare. 



Living shells in Barren Brook, one quarter of a mile below the 

 marl deposit, in a small pond on the brook, the land shells obtained 

 at the water's edge. 



Succinea obliqua Say. Rare. 



Succinea ovalis Gld. Common. 



Succinea avara Say. Rare. 



Strobilops labyrinthica Say. 



Bifidaria pentodon Say. 



Vertigo ventricosa Morse. 



Conulus fulvus Mull. 



Zonitoides arboreus Say. 



Zonitoides exiguus Stimp. Common. 



Carychium exile Lea. Common. 



Physa heterostropha Say. Rare and small. 



Limnaaa desidiosa Say. Small compared with the fossils. 



Planorbis trivolvis Say. Abundant. 



Planorbis parvus Say. Common. 



Planorbis crista Linne, var. cristata Drap. Common. 



Anodonta fragilis Lam. Rare. 



Sphaerium simile Say. Common in the brook below the pond. 



Sphasrium rhomboideum Say. One small living specimen. 



Pisidium abditium Hald. Rare. 



Pisidium compressum Prime. Few where the road crosses the 

 brook. 



Pisidium rotundatum Prime. Rare. 



Pisidium splendidulum Sterki. Abundant ; type locality. 



Pisidium variabile Prime. Abundant. 



Pisidium seminulum Sterki?. Few specimens referred to this 

 species. 



Pisidium ventricosum Prime. Common. 



Pisidium walkeri var. mainense. Common. 



