. The Canadian field-naturalist. January, 1922.] The Canadian Field-Naturalist. (Trans. 1, p. 40) contains only four species, two of which were not positively identified. Another species was added in the Report of the Concho- logical Branch, read March 13, 1890, and prepared by the writer and the late Rev. Geo. W. Taylor, which gives a catalogue of all the molluscs then known to be found in the vicinity of Ottawa. The success attending Roper and Winkley in Massachusetts and Maine and the encouragement extended by Dr. Sterki induced me to devote special attention to this genus. The result was t
. The Canadian field-naturalist. January, 1922.] The Canadian Field-Naturalist. (Trans. 1, p. 40) contains only four species, two of which were not positively identified. Another species was added in the Report of the Concho- logical Branch, read March 13, 1890, and prepared by the writer and the late Rev. Geo. W. Taylor, which gives a catalogue of all the molluscs then known to be found in the vicinity of Ottawa. The success attending Roper and Winkley in Massachusetts and Maine and the encouragement extended by Dr. Sterki induced me to devote special attention to this genus. The result was that in my Preliminary List of Sphaeriidae published in The Naturalist in 1913, I enumerated twenty-three species of Pisidia, several of which were considered new. Since then I have added several others and the field is by no means ex- hausted. So numerous are the localities in which the shells occur that many other species and varie- ties must remain undiscovered. 33. PisiDiUM VIRGINICUM Gmelin.—Heron found this shell on the beaches of Kettle Island exposed at low water. My only specimens were obtained in a similar situation lower down the Ottawa, and by dredging in the pond, prolific in small molluscs, on Duck Island— near the south end. With the p. virginicum, X 2 exception of P. idahocnse., which has not been found in Ontario or Quebec, it is the largest known species, attaining frequently a length of 8 mm. It appears to be quite active and makes long and distinct furrows in moving. When mature it is always of a dark brown color near the umbones. Mr. A. D. Robertson found P. virginicum abundant in sandy channels in the Georgian Bay (Contributions to Canadian Biology, Fasc. ii, 107), but appears not to have noticed there any other shell of the genus. The species has a wide range in the United States east of the Rocky Mountains, and extends even into Alaska and Yukon. 34. PisiDiUM idahoense Roper. This shell ranges from Idaho westward to Washington and northward through Br
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