[13] INSTEUCTIONS FOE COLLECTING MOLLUSKS DALL. 



Viviparidce, Ampullaria^ and Hydrohiince; in ponds and sluggish 

 streams Flanorhis, Limncea, and Amnicola abound; estuaries afl'ord 

 Corhiculaj Gyrena, and Melanopsis, beside sucli modified marine species 

 as Azardf Tagelus, some Rissoidce, Neritina, and Bithmia, and occa- 

 sionally half marine Gyrenoidea and Psammohiidce. Swift streams often 

 teem with Melanians of diiferent genera, and under their pebbles lurk 

 fresh-water Neritina^ Planorbis, and Ancylus. Lily x^ads are a good 

 collecting ground for small specimens, and in the tufts of water-loving 

 grasses as well as the soft mud about their roots numerous moUusks 

 may be found. 



OUTFIT. 



For carrying the larger bivalves a bag or basket is convenient and 

 a dip net with rather wide meshes will enable the collector to search 

 soft mud for bivalves or pick up IsTaiades from water too deep for the 

 arm alone. A few vials for the smaller species, a tin water pail for 

 preserving interesting forms alive, a thin-bladed knife for roughly 

 cleaning large bivalves, and the ever useful forceps will make an outfit 

 quite sufficient for the collector's needs. 



FAVOE,ABLE LOCALITIES. 



The preceding remarks will have indicated places where search may 

 loreferably be made. The drift along river and lake beaches and the 

 vicinity of muskrat burrows will often afford dead sx)ecimens in good 

 condition. Trailing weeds and the long fibrous roots of trees often con- 

 ceal rarities in their meshes. 



EGGS. 



The eggs of fresh-water gastropods are often deposited in little masses 

 of clear jelly, which may be preserved in fresh water and reared in an 

 extemporized aquarium. Goldfish globes or thin jars of plain glass 

 are quite as good and much cheaper for such purposes than the more 

 pretentious metal-framed aquaria for sale by dealers. 



ENEMIES AND PARASITES. 



The muskrat and the wild duck feed largely on mollusks. In the 

 crop of the latter and about the burrows of the former specimens still 

 suitable for study may often be found. The embryos of fresh- water 

 bivalves are often provided with temporary booklets, by which they 

 adhere to the fins of small fishes or the legs of other water animals, and 

 are thus transi3orted from one pool or stream to another. In the gill 

 pouches of many species the young remain until their development is 

 well advanced. This is especially the case in the Unionidce, and the 

 swelled organs in their season are often very remarkable and offer an 

 inviting field for special study. The sexes are separate, and as the 

 growth of the shell goes on during the gravid season its form in the 

 female is often modified by the mechanical pressure of the soft parts, so 



