342 LAND AND FRESHWATER MOLLUSCA OF MANITOBA. 



as aquatic species, in astonishing abundance, are found in all 

 the ponds, lakes, sleughs, and streams. 



Most of my collecting was done in the vicinity of the town 

 of Carberry, which is surrounded by a dry, level prairie, known 

 as the Big Plain. Others of my specimens I obtained from the 

 many moist spots or ponds occupying the hollows of the rolling 

 prairie around the City of Brandon ; others from the innumer- 

 able ponds and lakes everywhere dotting the country between 

 Brandon and Fort Ellice ; others from depressions in the level 

 sandy prairie south of Beaver Creek, near Fort Ellice ; while 

 others are from the Red River, the Souris, and the Assiniboine. 

 One great feature of the prairie-region, of which Manitoba forms 

 part, is the extraordinary number of lakes and lakelets. Their 

 number is enormous, especially in some localities. They are 

 of 'all sizes from the dimensions of one's sitting-room up to the 

 size of Lake Winnipeg ; but the most common size is from 

 one-quarter to half-an-acre. The smaller ones dry up com- 

 pletely during the summer and autumn ; while the water in the 

 larger ones becomes greatly lowered, to be raised again by the 

 melting of the snow in the spring. Myriads of mollusks must 

 come into existence every spring, only to be killed by the drying 

 up of the ponds later in the year. To such an extent is this the 

 case that one is almost led to wonder that their extermination 

 does not ensue. When crossing, last October, the wide stretch 

 of level sandy prairie south of Beaver Creek, I was surprised to 

 find the ground strewn for long distances — often a mile or a mile 

 and a half — with bleaching fresh-water shells, showing clearly the 

 extent of the waters in the spring-time, though I saw but few 

 pools. Limncea palustris was the commonest species under these 

 conditions ; but, in the deeper depressions, where rushes grew, 

 there were others, including Bulinus hypnorum, Sphmriuni 

 jayanum, Planorbis exacutus, &c. A sleugh is a marshy spot or 

 pool on the surface of the prairie, often occupying the bottom of 

 a coulee or old watercourse. "The Swamp," more than once 

 referred to, is a large extent of almost impassable virgin swamp, 



J.C.iv., July, 1SS5. 



