374 THE CHICAGO ACADEMY OF SCIENCES. 



the edge, white; inner lip reflected so as to nearly cover the umbilicus 

 leaving a very small chink ; parietal callus thick, wide, white, columella 

 with a rather heavy thickening in the center which forms a conspicu- 

 ous plait; the axis is very slightly twisted. The varical bands on the 

 shells examined are obscured by the thickness of the shell. 

 Length. Width. Aperture length. Width. 



16.50 8.50 8.10 4.50 mill. James Bay. 



15.00 8.00 8.00 3.90 " 



14.25 7.50 7.10 3.50 " 



14.50 8.00 7.50 3.90 " 



11.50 6.10 6.10 3.25 " 



10.00 6.00 " Arctica ex Tryon. 



TYPE: The type is not in the Smithsonian Institution. 

 TYPE LOCALITY: Moose River, near Hudson Bay. 

 ANIMAL, JAW, RADULA and GENITALIA: Not recorded. 

 RANGE: (Figure 43) James Bay, northwest to Great Slave Lake. 

 Arctica is typically a boreal form (Canadian division) which has not 

 been found south of the fifty-first degree of north latitude and appears 

 to be confined to the Hudsonian and Mackenzian regions. Additional 

 records will doubtless fill in the blank territory on the map. 



RECORDS. 



ONTARIO: Moose River (Lea); Moose River, Hudson Bay (Drexler; 

 Nason) ; Hudson Bay (Walker) ; two miles above mouth of Harricanaw River, 

 Hannah Bay (O'Sullivan and Spreadborough ; W>hiteaves). 



MACKENZIE: Fort Rae, Great Slave Lake (S. Jones); in crop of duck, 

 Great Slave Lake (Preble). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY: Not recorded. 



REMARKS: Arctica may be recognized by its thick, heavy shell 

 and heavy plaited, almost toothed columella. In most of the speci- 

 mens examined the fourth whorl is disproportionately large, a feature 

 not observed in vahlii or pingelii. A part of the original lot of arctica 

 received from Drexler is figured on plate XXXIX, (figures 20-23). 

 They agree perfectly with Lea's description. The figure given by 

 Tryon in his continuation of Haldeman's Monograph is very poor and 

 does not correctly represent this race. 



Galba vahlii pingelii ("Beck" Holler). Plate XXXIX, figures 

 24-27. 



Limnaa (Limnophysa) pingelii BECK, Index, p. Ill, 1838. 



Limnaa pingelii (Beck) MOLLER, Index Moll. Groen., p. 5, 1842. 



Limna>a pingelii BINNEY, Check List, p. 12, 1860; L. & F.-W. Sh. N. A., 

 II, p. 58, fig. 90, 1865. MORCH, Amer. Journ. Conch., IV, pp. 35, 37, 1868. 

 SOWB., Conch. Icon., XVIII, sp. 98, pi. 14, fig. 98, 1872. 



Lymnaa pingelii SCUDDER, Bull. Nat. Mus., 23, p. 201, 1885 



