324 Illinois State Laboratory of Natural History. 



several others the ground has scarcely been broken, save by 

 the brief and miscellaneous descriptions of new species. As 

 in all such miscellaneous work there has been much looseness 

 of definition and probably partial or complete re-description, 

 many of the species as given in the following list will ulti- 

 mately be reduced to synonyms or otherwise disappear from 

 sight. While we deplore this looseness we cannot wholly 

 ignore work because it has been poorly performed, as some of 

 our recent carcinologists have been prone to do. 



The species of fresh water Crustacea, as given herein, com- 

 prise 313 names, distributed in 88 genera and 29 families, as 

 follows : 



As to the relative abundance in the different sections of 

 the country, too little is now known of the range of individual 

 species to form any satisfactory conclusions. The following 

 geographic table will, therefore, show the comparative amount 

 of attention each group has received in different sections 

 rather than an exact representation of geographic distribution : 



