1917] The Ottawa Naturalist. 19 



on the Point. 



This stretch of woods is the richest collecting ground for snails 

 in the neighbourhood, particularly the maple-beech area just men- 

 tioned, which is the only spot where Omphalina inornata (Say) was 

 found and where Polygyra tridentata (Say) and P. palliata (Say) are 

 common. Omphalina fuliginosa (Griffith), Vitrea multidentata 

 Binney and Philomycus carolinensis (Bosc.) were also frequently met 

 with here but not often seen elsewhere. 



The low land on the northwest side of the ridge extends to the 

 lake on the north shore and its increasingly swampy soil is indicated in 

 the gradual change in its tree growth' from a mixture of poplar, birch, 

 cedar, balsam fir, white pine and white spruce, etc., to a nearly pure 

 stand of tamarack. In the opposite direction it passes into a somewhat 

 open stand of poplar and birch with scattered conifers and other trees. 

 This portion is a good place for many species of snails, certain forms 

 such as Polygyra thyroides (Say) and P. albolabris (Say) being par- 

 ticularly common. Elsewhere this wood is very dense and not very 

 productive of Mollusca, particularly in the tamarack swamp. 



Half a mile west of the apex of the "Point" is a wide open marsh 

 traversed by a sluggish creek, from which an interesting zonal dis- 

 tribution of vegetation can be traced back to the sandy ridge already 

 mentioned. The creek rises in a small wooded ravine less than half a 

 mile to the southwest and, until it reaches the open marsh, is a mere 

 brook, following a devious course through woods, pastures and alder 

 thickets. 



The soil of De Grassi Point and the surrounding country is 

 everywhere deep, there being no outcroppings of the bed-rock ( Trenton 

 limestone) but the higher parts are all plentifully bestrewn with 

 boulders, chiefly of Laurentian gneiss. 



It will be seen from the foregoing account that in spite of the 

 general flatness of the district a considerable variety of conditions 

 obtains in a very limited area (less than one square mile) and. from a 

 long acquaintance with the surrounding country I believe that nearly 

 all the species of land Mollusca to be expected there will be found to 

 occur at De Grassi Point or its immediate vicinity. 



In the determination of the species of the following list I take 

 pleasure in acknowledging my indebtedness to Mr. Bryant Walker of 

 Detroit, Mich., who kindly examined the forms of whose identity I 

 was in doubt. These included the species of Vertigo, Euconulus, 

 Strobilops and Gastrodonta and several of Vitrea and Bifidaria. My 

 determination of Arion circumscriptus Johnston was kindlv verified by 

 Dr. H. A. Pilsbry. 



Since this paper was prepared for the press some additional 

 collecting was done at De Grassi Point between April 27th and May 



