cross the museum to study these snails, as they belong to a different 

 order from the air-breathers." 



In a few moments, we had walked to the opposite side of the 

 museum and had gathered around the case which the Professor had 

 pointed out to us. All became silent and eagerly listened, while the 

 Professor continued : 



" Among the most common of this order are the river snails known 

 as Strepomatids. There are about three hundred species in this family, 

 and with two or three exceptions they are confined in geographical 

 distribution exclusively to the United States. The shells are very 

 graceful, having long, turreted spires of ten or twelve whorls, and 

 small apertures. The color of the shells is generally a uniform greenish 

 or yellowish, although some species have color bands, and the aperture 

 is frequently tinged with purple or red. It is an interesting fact that 

 the majority of the species of this family are found in the rivers and 

 streams of Tennessee, Alabama, Ohio, West Virginia, and Mississippi. 

 From these states a few species have migrated to the east, west, and 

 north, and are now found in almost every part of the United States. 

 You will see by the number of shells exhibited in this case what a 

 variety of species occur in this family. 



" A family closely allied to the last is the Melaniidce, the animals 

 of which inhabit the entire world, except North America. They may 

 be distinguished from the last family by the presence of little finger- 

 like digitations on the edge of the mantle, similar to those in Physa. 

 The shells are generally larger and more highly colored than those 

 of the Strepomatids, many of them being of a dark chocolate color, 

 while some are a beautiful glossy black ; some shells are smooth, 

 while others are ornamented by knobs and spines. The genus Melania 

 is the most characteristic form. Some species are viviparous, like the 

 apple-snails. 



" The largest and handsomest of the fresh-water snails belong to the 

 two families, Viviparidce and Ampulariidce, the shells of the latter 

 family frequently attaining a length of three inches. The animals 

 of the first family prefer a sandy beach in a large lake or river, 

 while those of the second generally live in more or less muddy rivers, 

 ponds, and creeks. A single genus of Viviparidce, Campeloma, is con- 

 fined solely to that portion of the United States east of the Rocky 

 Mountains. The shells are generally of a rich grass -green, and in 

 certain localities they may be collected by thousands. 



" Unlike many of the snails at which we have been looking, this 

 family is viviparous; that is, it brings forth its young alive instead 



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