BULLETIN 
OF THE 
ILLINOIS MUSEUM OP NATURAL HISTORY, 
l^TTIMIIBEIR, X. 
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 S. I. Smith of Yale College for specimens and for suggestions concern- 
ing the species of Eubranchipus 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. stygius , Bundy. “ Male. Rostrum long, triangular, smooth above, 
small teeth near apex, foveolate at base ; carinae parallel, separated from base 
of rostrum by slight grooves; cephalo-thorax somewhat compressed, smooth 
or slightly punctate above, granulate on sides, areola narrow, smooth ; 
