BTJLLETIISr 



OF THE 



ILLINOIS MUSEUM OF NATURAL HISTORY. 



LIST OF ILLINOIS CRUSTACEA, 



WITH DESCRIPTIONS OF NEW SPECIES. 



By S. A. FORBES. 



The following list is to be regarded as only a first contribution to the 

 knowledge of our Crustacea, as it presents the results of a single season's 

 work. Considering the fact that, while our streams and pools are populous 

 with interesting forms, many of which are new, only a single species outside 

 the genus Cambarus has heretofore been credited to the state, it is hoped 

 that even so imperfect a paper as this may not be without its uses. 



I wish to acknowledge especial obligations to Professors A. E. Verrill 

 and 8. I. Smith of Yale College for specimens and for suggestions concern- 

 ing the species of Eubranchlpus and Crangonyx described herein, and to 

 the latter of these gentlemen for many other favors. 



Cambarus acutus, Gir. Very common in central Illinois. Taken in 

 large numbers at Normal and Pekin. Of '25 males examined, the first ab- 

 dominal legs were all those of Hagen's variety A. In none was the epistoma 

 pointed, and a distinct lateral thoracic spine was present in but one. In 

 twenty of the specimens the margins of the rostrum were distinctly convex 

 from the base to the apical teeth ; and the latter were in all much smaller 

 than in Hagen's figures, the distance across the teeth being but one-fourth 

 to one-third that across the base of the rostrum between the tips of the 

 spurs. The tubercle in the basal foveola was elongated, notched in front 

 and continued backward into a very slight cephalo-thoracic carina. Be- 

 tween the posterior callosities and the transverse line, the cephalo-thorax 

 was finely rugulose. The females observed were also variety A. 



C. stj/ffius, Bundij. " Male. Rostrum long, triangular, smooth above, 

 small teeth near apex, foveolate at base ; carinoe parallel, separated from base 

 of rostrum by slight grooves; cephalo-thorax somewhat compressed, smooth 

 or slightly punctate above, granulate on sides, areola narrow, smooth ; 



