152 Illinois State Lahoratorij of Natural History. 



forth alive, and may be found in the ovaries in the fall preced- 

 ing the spring during which they are set free. The adults go 

 into the mud at the bottom of the ponds and streams to hiber- 

 nate. 



Localities: Harkness Slough, Quincy Bay, Willow Slough, 

 Lily Lake, Broad Lake, Wood Slough. 

 Lioplax siibcariiiata, Say. 



{Limna'a suhcarinata, Say, Am. ed. Xich. Enc. 1, 1816.) 

 Frequent in Willow Slough. Similar to the preceding, but 

 smaller and marked by an obtuse ridge extending along the 

 middle of each whorl. One of the largest examples taken is 

 just .50 inch in length. Like the other members of the family 

 it is viviparous. 



Family Rissoid^. 



Somatogyrr{s isogonus^ Say. 



{Melania isogona, Say, New Harmony Disseminator, ii, 

 227, i829.) 



Numerous examples from Willow Slough, Aug. 15. 

 Amnicola limosa^ Say. 



( Paludina limosa, Say, Jour. Acad. Nat. Sci. Phil., i, 125, 

 1817.) 



Dredged in 3-5 feet of water, Willow Slough, Aug. 15. 



The clams are not very different from the river snail^ in 

 their way of living. They may be frequently seen in shallow 

 water with the front part of the body buried in the mud and 

 the soft, white "foot" thrust out of the shell. If watched in- 

 tently under such circumstances they may be observed to move 

 slowly forward, leaving a groove in the mud behind them. In 

 suitable places in quiet water they may become very abundant, 

 forming what are known as clam beds. The food of some of 

 our species consists entirely of microscopic plants and animals, 

 such as algae and protozoans. Some of the Unios are very 

 probably scavengers, if we may decide from the condition of 

 food in the stomachs of alcoholic specimens. In winter our 

 species probably all go into the mud at the bottom of the 

 streams and lakes, and there remain torpid until spring. 



Their interest, viewed either from the standpoint of the 

 fish-culturist or from that of the scientist, is very great. As 



