February, 1920] 



The Canadian Field-Naturalist 



33 



5. occidentale does not extend as far to the north 

 as S. rhomboideum. It ranges however in a belt of 

 irregular width from Quebec and the Eastern States 

 to California and British Columbia. 



7. SphAERIUM TORSUM Sterki was described 

 from shells collected in Moore's Creek m the same 

 station that affords 5. aureum. I have not found 

 it elsewhere. Dr. Sterki may, however, have speci- 

 mens among shells sent to him from the Rideau. If 

 so the fact escaped my notice. By his permission — 

 one of many sets of kindness — I append his descrip- 

 tion: — 



Sphaerium iorsum sp. nov. 



Mussel inequipartite, oblique, well-inflated, poster- 

 ior part higher, and much more voluminous than the 

 anterior; dorso-ventral axis curved and oblique; 

 beaks strongly inclined forward, large, promment, 

 rounded, not or slightly, mamillar, superior margin 

 curved, not, or barely, bounded by angles ; scutum 

 and scutellum well marked ; anterior and posterior 

 ends rounded, inferior margin moderately curved ; 

 surface with fine, slight, irregular or subregular con- 

 centric striae and a few lines of growth, shining ; 

 yellow, straw colored in younger specimens ; shell 

 moderately strong, hinge long for the shape and size 

 of the mussel, almost regularly curved, ''ather slight; 

 cardinal teeth small, the left posterior tooth vestigial 

 in some specimens ; laminae rather slight, at almost 

 right angles to edch other; ligament covered, resilium 

 moderately strong. Soft parts not examined. Long. 

 II mm.; alt. 9 mm.; diam. 7 mm. (100: 83:64). 



5. Iorsum appears to range near emarginatum of 

 the same region, but is more oblique, of more round"d 

 outlines, more evenly inflated. The beaks are less 

 elevated, less mamillar, and more inclined forward, 

 and the hinge is much slighter. 



Habitat. — Quebec, Ontario, along the Ottawa 

 River near Hull and Ottawa, collected by Justice 

 Latchford. No. 6956 for full-grown, and 7286 

 for young and adolescent specimens. It occurs also 

 in Wisconsin. 



Fossil. — ^Goat Island, Niagara, collected by Miss 

 J. E. Lotson, 1900, (No. 2224a). 



8. Sphaerium emarginatum Prime ranges 

 from Maine to Lake Superior and Winnipeg, and 

 northwest to the District of Patricia, where it was 

 found by Mr. Mclnnes in the Attawapiscat river. 

 Mr. James H. Ferris found it in great numbers in 

 the Montreal river, north of Sault St. Marie, and 

 has kindly sent me specimens from that locality. 



In the vicinity of Ottawa this species has been 

 found only in the canal, above Hartwell's locks, and 

 in the outlet of Phillip's lake, in the County of Pon- 

 tiac. Its resemblance to torsum is indicated in the 

 description of that species. The Ottawa shells are 

 slightly more inflated, the average size from the canal 

 being 10.2 x 8 x 7 mm. 



9. Sphaerium stamineum Conrad does not 

 seem to be a common shell in or near Ottawa, where 

 I have not found it elsewhere than in the Rideau 

 opposite Strathcona Park. In Toronto it abounds in 

 the Don and Humber. The beautiful little Lynn 

 between Simcoe and Port Ryerse, in the County of 

 Norfolk, also affords it in great numbers. 



A shell doubtfully considered stamineum, but 

 which may be an undescribed species, occurs in the 

 outlet of Swan lake in Pontiac. Unfortunately 

 only a few could be procured. 



S. stamineum is approximately triangular in out- 

 line and of a uniform yellow color. The name ap- 

 plied to it by Conrad (meaning thready or fibrous) 

 does not refer to any of its characteristics. Probably 

 stramineum (=stra-a>^) was the term intended, as 

 that is the prevailing color of the species; but as 

 the specific name applied has some meaning it must 

 stand for all time. Toronto shells average 13.5 x 10 

 X 9.7 m.m. 



10. Sphaerium acuminatum Prime. A mus- 

 sel believed to be this species is very common in 

 Lake Des Chenes, especially above the pier at 

 Britannia and in Graham Bay. Prime at one time 

 at least regarded acuminatum as a synonym of s^ri- 

 atinum; but no form of the latter species that I have 

 ever seen approaches in appearances the Des Chenes 

 shell when mature, though young shells are not un- 

 like young striatinum. 



In midsummer dead shells may be occassionally 

 noticed washed up along the railway embankment at 

 the southerly end cf the bay. Later, when the river 

 is in its lowest state, thousands of this species rise 

 from their drying beds all over the exposed flats, 

 and plough along the surface their slow way — 

 devious at times but in the main direct — towards 

 the receding water. This manifestation of the in- 

 stinct of self preservation is common to all mussels, 

 large and small, in similar condition; but I know of 

 no place in which it is more plainly exhibited than 

 in Graham bay. The furrows end in a deeper de- 

 pression when the animal is exhausted or has reached 

 a location sufficiently moist. The number of speci- 

 mens that one can collect is limited only by the 

 time at one's disposal. Children learn quickly where 

 the shells are to be found, and delight in picking them 

 up and rendering aid to the naturalist who desires 

 a large series of specimens. Identification is ren- 

 dered easy owing to the fact that no other Sphae- 

 rium has been found in the bay. Many pisidia how- 

 ever ocur there — of which more hereafter; and south 

 of the railway, in the marsh, connected at high water 

 with the bay through a culvert, several species of 

 our three genera of sphaeridac are to be found in 

 early summer. 



Eighty or ninety shells found on June 21, 1916, 

 between little islets, near the shore, about five hun- 



