It is under the influence of these general ideas that I propose to examine briefly to-night the lacustrine life of Illinois, drawing my data from, collections and observations made during recent years by myself and my assistants of the State Laboratory of Natural History.

Genus Cycleptus Rafinesque ', C. elongatus (Le Sueur). Missouri Sucker Genus Ictiobus Rafinesque I. cyprinella (Cuvier & Valenciennes). Red-mouth Buffalo I. urus (Agassiz). Mongrel Buffalo 70' I. bubalus (Rafinesque). Small-mouth Buffalo Genus Carpiodes Rafinesque C. carpio (Rafinesque). Common River Carp C. difformis Cope. Blunt-nosed River Carp C. velifer (Rafinesque). Quillback C. thompsoni Agassiz. Lake Carp Genus Erimyzon Jordan 80 E. sucetta oblongus (Mitchill). Chub-sucker Genus Minytrema Jordan M. melanops (Rafinesque). Spotted Sucker

Mr. H. L. Ashlock of this firm expressed at this time his belief that a distinct sturgeon, known to the fishermen of the locality as the "white sturgeon," was occasionally obtained among the catches of the common shovelnose locally called the"switch-tail," an opinion presently confirmed by the receipt of one specimen of this species and the head of another, brought in by his fishing crews.

This paper is thus to be taken as a contribution to an answer to the following questions: What Illinois fishes are habitually found in each others' society,and what is the relative frequency of their associations? How are Illinois fishes grouped and distributed according to location and situation, and in each ecological assemblage so formed what is the proportionate representation of its various constituent species? How far are the two classes of data^ those of associative affiliation and of ecological relationship, comparable, and to what extent may the one be used to explain the other?

No abstract