544 



region — excluding the Lake Michigan series (for which the lakes are 

 too small and warm) and those peculiar to creeks and rivers. Possibly 

 the relative scarcity of catfishes { Sihiridcie) is due to the comparative 

 clearness and cleanness of these waters. 1 see no good reason why min- 

 nows should be so few, unless it be the abundance of pike and Chicago 

 sportsmen. , 



Concerning the moUuscan fauna, I will only say that it is poor in 

 bivalves — as far as our observations go — and rich in univalves. Our 

 collections have been but partly determined, but they give us three spe- 

 cies of Valvata, seven of Planorbis, four Amnicolas, a Melantho, two 

 Physas, six Limnseas, and an Ancylus among the Gastropoda, and two 

 Unios, an Anodonta, a Sphserium, and a Pisidium among the Lamelli- 

 branchiates. Pisiduim variabilc is by far the most abundant moUusk 

 in the oozy bottom in the deeper parts of the lakes; and crawling 

 over the weeds are multitudes of small Amnicolas and Valvatas. 



I'he entomology of these lakes I can merely touch upon, mention- 

 ing only the most important and abundant insect larvae. Hiding under 

 stones and driftwood, well aware, no doubt, what enticing morsels they 

 are to a great variety of fishes, we find a number of species of ephemerid 

 larvae whose specific determination we have not yet attempted. Among 

 the weeds are the usual larvae of dragon-flies — Agrionina and Libellu- 

 lina, familiar to every one ; swimming in open water the predaceous 

 larvae of Corethra; wriggling through the water or buried in the mud 

 the larvae of Chironomus— the shallow water species white, and those 

 from the deeper ooze of the central parts of the lakes blood-red and 

 larger. Among Chara on the sandy bottom are a great number and 

 variety of interesting case-worms — larvae of Phrj'ganeidae — most of 

 them inhabiting tubes of a slender conical form made of a viscid secre- 

 tion exuded from the mouth and strengthened and thickened by grains 

 of sand, fine or coarse. One of these cases, nearly naked, but usually 

 thinly covered with diatoms, is especially worthy of note, as it has been 

 reported nowhere in this country except in our collections, and was in- 

 deed recently described from Brazil as new. Its generic name is 

 Lagenopsyche, but its species undetermined. These larvae are also eaten 

 by fishes. 



Among the worms we have of course a number of species of leeches 

 and of planarians, — in the mud minute Anguillulidae, like vinegar eels, 

 and a slender Lumbriculus which makes a tubular mud burrow for itself 

 in the deepest water, and also the curious A'ais probiscidca, notable for its 

 capacity of multiplication by transverse division. 



The crustacean fauna of these lakes is more varied than any other 

 group. About forty species were noted in all. Crawfishes were not 

 especially abundant, and most belonged to a single species, Cambarus 

 virilis. Two amphipods occurred frequently in our collections; one, 

 less common here but very abuniiant farther south — Craiujoiiyx (jiacilis — 

 and one, Allorchestes dcntata, probably the commonest animal in these 

 waters, crawling and swimming everywhere in myriads among the sub- 



