XVII. SOME DIRECTIONS AND SUGGESTIONS FOR COL- 

 LECTING THE SPH.E:RIID^ AND AQUATIC 

 GASTROPODS. 



By Victor Sterki, M.D. 



The Sphseriidae, our smallest fresh-water Pelecypoda, or bivalves 

 (mussels), are very interesting objects of study. They have been 

 somewhat neglected on account of their generally small size and the 

 apparent difficulty of securing them. They are also somewhat 

 difficult to identify, principally because of the considerable variation 

 which reveals itself among them. At present there are over two 

 hundred species and varieties known from North America, belonging 

 to the genera Sphcerium, Musculuim, Eiipera, and Pisidium. Their 

 many varieties and forms make them all the more interesting, because 

 ■of the questions which they raise as to systematic arrangement and 

 ■ distribution. The largest are about 20 mm. long {SphcErium sul- 

 catum); the smallest 1.5-2 mm. {Pisidium piinctatum, and some 

 <others) . 



They are approximately well-known from only some small parts 

 ■of the continent. Few places have been systematically and thoroughly 

 tsearched, and there are stretches of hundreds and thousands of square 

 miles where only a little sporadic collecting has been done, and 

 •equally large areas in which no collections at all have been made. 

 There are therefore chances almost anywhere to secure valuable 

 material for a collection and at the same time to aid the specialist 

 in studying them. The same, to a large extent, may be said of the 

 aquatic gastropods, or snails. They are generally associated, and 

 the methods of collecting them are essentially the same. 



U'here Found. 



They live in waters of all kinds, and no place should be neglected ^ 

 ■or overlooked, especially since different species and forms are found 

 in different habitats. Lakes, ponds, rivers, and sloughs, canals, 

 ditches, springs, and even the smallest rills, sink-holes, swamps, and 

 marshes, even miry puddles, all yield some of these mollusks. Waters 



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