32 



The Canadian Field-Naturalist 



[Vol. XXXIV. 



the Little Chaudiere rapids, at least along the Ont- 

 ario shore, any bright little bivalve found there may 

 safely be designated S. flavum. 



5. Sphaerium RHOMBOIDEUM Say is a shell of 

 great beauty and very wide distribution, its range 

 extending from the New England States to Alaska. 

 The most northerly locality recorded for this prov- 

 ince is Albany river, where it was collected by Mr. 

 Mclnnes. 



The specific name, like many of the names ap- 

 plied by the famous naturalist who described it, ex- 

 presses the most striking characteristic of the species. 

 Certain other sphaeria are rhomboidal in lateral 

 outline ; but none appears so obviously to have that 

 form. Other features renders this species readily 

 distinguishable. The epidermis is highly polished, 

 usually dark olive in color, with lighter bands and 

 an outer yellow zone. In a few localities, however, 

 it is of a uniform deep brown. This is especially a 

 marked feature of the shells from the pond on Duck 

 Island, and, to a less extent, of those from the pond 

 on the Metropolitan Electric Company's property at 

 Britannia. Iron in the water may have brought 

 about this effect. No other cause can in my opinion 

 be suggested for the brown color not only external 

 but incorporated in the substance of the shell of the 

 lymnaeidae which swarm in the bay, opposite the 

 Rideau falls, into which Leamy lake discharges 

 "the Rafting Ground" of other times, where the huge 

 sticks of white pine, made in the charttiers of the 

 Wrights, McGoeys, and Hamiltons, were after their 

 perilous drive down the chutes and cataracts of the 

 Gatineau, formed into cribs and rafts in the spacious 

 days of the square timber trade. Either from rusted 

 chains, iron implements long lost in the bay, or from 

 leachings from the mines and furnaces once operated 

 a few miles to the north, every shell there acquires a 

 coat of brown mail, and many become dwarfed in 

 growth. Planorbis antrorsus has not a tenth of the 

 volume of shells of the same species found among the 

 nearby hills; and PL campanulaius is even smaller 

 than the depauperate form from the marl beds at 

 Hemlock Lake. S. rhomboideum, as it occurs not 

 in the bay, but in the canal leading into it from 

 Leamy lake, is not seriously affected, though browner 

 than any found elsewhere except at Britannia and 

 on Duck island. 



This species was once very common in the ponds 

 north of St. Louis' Dam, and is doubtless still to be 

 found in Dow's lake, south of it. Farther to the south 

 it ocurs in the outlet of Dow's swamp. To the east 

 it is found in Hemlock lake, but not in large num- 

 bers. The most easily accessible and productive 

 locality for it is the creek in Britannia Highlands, at 

 the Bridge on Tavistook Road. It may, however, be 

 met with in almost any stream or pond on the On- 

 tario side of the Ottawa. In the clearer waters of 



the Laurentian hills it seems to occur but rarely. One 

 specimen has been found in Meach lake, and none 

 elsewhere on the Quebec side. An adult shell of 

 average size measures 13x10x9 mm. Young shells 

 are proportionably less inflated. 



6. Sphaerium occidentale Prime. This is one 

 of our commonest species. It may be found in almost 

 any marsh, or any depression in our deciduous 

 woods where water lies at intervals. Many of the 

 sphaeriidae are capable of enduring long periods of 

 dessication more apparent at times than real, as 

 some moisture will on careful investigation be often 

 seen to be present; but this species can seal up its 

 activities and lie dormant for weeks or months in 

 the driest situations. Of course all molluscs living 

 in our marshes, and shallow creeks, and ponds, are 

 frozen stiff as icicles every winter; but except in 

 winter comparatively few can remain long alive 

 without water or at least moisture. S. occidentale 

 can better endure a long period of absolute drought, 

 such as sometimes prevails in Ontario, especially in 

 recent years, than any of the genus. None of our 

 large bivalves seems capable of enduring dessica- 

 tion for more than a few days or at most a week; 

 though certain Florida kinds have been found alive 

 by Charles T. Simpson in stations which had long 

 been as dry as dust. 



In the woods in the Eastern part of the City, near 

 Beechwood cemetery, every hollow contains this 

 Sphaerium and no other. In midsummer it may be 

 found in such places by raking the surface of the 

 mould. It is usually bright yellow, oval in outline, 

 but slightly inflated, and seldom exceeds 8 mm. in 

 length. A much paler form ocurs on Lemieux island, 

 south of the new pumping station. It is a clear 

 Naples yellow in color, but does not vary from the 

 normal in any other respect. At Britannia where 

 S. occidentale exists in great numbers in the marsh 

 in Loma Park, near the Magee farm, and, on that 

 farm, north of the railway lines, in a hollow under 

 large willows directly north of Britannia Highlands 

 station a locality singularly prolific in many desir- 

 able shells it is smoky grey in color. West of the 

 village it may be found inside the railway culvert. 

 In these and other stations it is accompanied by 

 several members of the family, and the beginner 

 would do well to procure first the shells of McKay's 

 bush or Lemieux island before resorting to places 

 where several sphaeriums and muscuhums are also 

 found. 



Under an inch objective this shell will be noticed 

 to be covered with numerous small papillae. This 

 feature has not been observed in any of our other 

 species, and may serve as a means of identifying 

 occidentale. Once however the characteristics of the 

 species are carefully observed, confusion with any 

 other known to occur near Ottawa is unlikely. 



