FAMILY PHYSID^E IOI 



? Section Macrophysa Meek. Shell elongate, columnar, large, the 

 last whorl and aperture small compared with that of the typical 

 Physa, the surface axially striated. Type Physa columnaris 

 Deshayes, Eocene of Paris Basin. 



Section Costatella Dall. Shell physiform, polished, sculptured with 

 axial ribs. Type Physa cos fata Xewcomb. 



The section Macrophysa has been affiliated to Isidora by Sandberger 

 and others, but as the species is only known in the fossil state some 

 doubt must remain as to its relations. It has somewhat the form of 

 Isidora 'wahlbergi Krauss from South Africa, but the resemblance 

 may be merely a parallelism and not an indication of relationship, as 

 we find several species of Isidora absolutely indistinguishable from 

 true Physa except by anatomical examination. 



The groups known as Ameria Adams, Glyptophysa Crosse, Plesio- 

 physa Crosse and Fischer, Physopsis Krauss, Pulmobranchia Pelsen- 

 ear, etc., are more or less intimately connected with Isidora Ehrenberg 

 (jBulinus Adanson) and do not form part of the family Physida. 

 None of them occurs in the region to which this paper relates. I am 

 indebted to the discussion of American Physaa by O. A. Crandall in 

 the Nautilus, volume xv, for assistance in determining the species of 

 Physa from the north. 



Physa heterostropha Say. 



Physa heterostropha SAY, Nicholson's EncycL, Am. ed. (no pagination), pi. 



i, fig. 6, 1817. HALDEMAN, Mon. Limn., p. 23, pi. n, figs. 1-9, 1843. 



BIXNEV, Land and Fw. Sh. N. Am., n, p. 84, figs. 144-5, 1865. 

 Physa plicata DE KAY, fragilis Mighels, lata Tryon, primeana Tryon, and 



philippii Kiister, are said to be synonymous by Crandall. 



Range. From the Potomac and Ohio Rivers 

 northward, and westward to the Mississippi. 



Anticosti Island ! Manitoba, Red River of the 

 North, Lac des Mille Lacs to Lake of the Woods ; 



Alberta, at Olds, McLeod and Red Deer. Grand ,? G ' 7 / 8 " 



' ' heterostropha. 



Rapids of the Saskatchewan ! L. Winnipeg ! English 

 River ! Albany River ! near James Bay ; Hudson Bay drainage in 

 Keewatin at Moose Factory ! and Nelson River ! Lake Isle Lacrosse ! 

 Peace River ! and Great Slave Lake ! 



Readily recognizable by its form and the absence of microscopic 

 spiral sculpture. The northern specimens, when dead, are of a beau- 

 tiful opalescent white with a claret colored apex. 



Physa gyrina Say. 



Physa gyrina SAY, Journ. Acad. Nat. Sci. Phila., n, p. 171, 1821. HALDE- 

 MAX, Mon. Limn., p. 32, pi. 3, figs. 1-6, 1843 ; Council Bluffs, Iowa. 



