1916 J The Ottawa Naturalist. 95 



contained in his collection and in the Carnegie Museum, Nos. 6,945 

 and 7,431. Justice Latchford writes in November, 1913: "No. 2,925 

 is quite common. I have visited the creek at all seasons and never 

 found any larger shells than those which I send; I therefore regard 

 them the larger ones as full-grown." 



[The creek referred to flows eastward through Britannia High- 

 lands, about four miles west of the city limits. Near the Shouldice 

 farm it affords remarkably large and beautiful specimens of 

 Sphaerium sulcatum.] 



13. Sphaerium torsum sp. nov. 



Mussel inequipartite, oblique, well inflated, posterior part higher, 

 and much more voluminous than the anterior; dorsoventral axis 

 curved and oblique; beaks strongly inclined forward, large, prominent, 

 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 concentric 

 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, rather slight; cardinal 

 teeth small, the left posterior tooth vestigial in some specimens; 

 lamina? rather slight, at almost a right angle to each other; ligament 

 covered, resilium moderately strong. Soft parts not examined. Long. 

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



5. torsum appears to range near emarginatum of the same region, 

 but is more oblique, of more rounded 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, 1911 and 1912. Types 

 in the collection of Mr. Latchford, and 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. Letson 

 1900 (No. 2224a). 



[Moore's Creek, on the Aylmer Road, north of the road, afford -; 

 large numbers of this species. | 



32. PlSIDIUM LATCHFORDI sp. nOV. 



Mussell small, inequipartite, oblique, nearly oval in lateral 

 aspect, well inflated; beaks somewhat posterior, rather large, promin- 

 ent, rounded; superior margin curved, supero-anterior slope slightly 

 marked, short, anterior end rounded, well below the longitudinal axis; 

 posterior part short, subtruncate, or rounded; surface slightly glossy, 

 with very fine and slight microscopic stria?, colorless to whitish, shell 

 translucent to opaque; hinge rather long, curved angular, stout, plate 

 rather broad, short; right cardinal tooth well curved, not much pro- 



