Mr. Stearns presented, in behalf of Mr. Rowell, the following description of a new species of Pisidium, collected during the field excursion to Angel Island:
Description of a New Species of Pisidium.
BY J. ROWELL.
Pisidium angelicum, Rowell.
Shell rounded oval, nearly equilateral, very convex; margin well rounded; beaks very slightly raised and very approximate; surface subgranulate, marked with from one to six very decided striæ or lines of growth; teeth too minute for observation.
Long. (of largest) 2 mill., Lat. 1.5 mill.; Diam. 1 mill.
Habitat: Angel Island.
Of California species, it is most like P. abditum, but differs in its sculpture, its less prominent beaks and its more globular and equilateral form. Most specimens are covered by an exceedingly persistent coat of jet black mud, making examination of them very difficult; but some are perfectly clean.
Mr. Stearns read the following note upon a recent