( 88 ) 
) 
Lepiopomus ischyrus and Eupomotis aureus. Another form which, from its 
variability, I have not yet ventured to describe as distinct from intermedium^ 
is very common in slow streams and fresh pools in McLean Co., especially 
in early spring, and has reached me also from La Salle *)p, and from Wis- 
consin. Its size is equal to that of communis , and it differs frokn typical in- 
termedins also in the much more robust development of all its apptfioJja^es, 
and in the large size of the second joint of the outer ramus of the second 1 
genital plates of the male. The form and proportions of these genital plates 
must be used with caution, however, in describing species, as they evidently 
vary greatly. 
Leptodora hyalina , Lilljeborg. 
This extremely curious crustacean, which may be known by its peculiar, 
slender form (that of a true cross, the arms of which are the swimming ap- 
pendages), by its extreme transparency and by the single eye in the front- 
end of its cylindrical head, has hitherto been observed in this country only 
• by Prof. S. I. Smith, by whom a single specimen was dredged in L. Su- 
perior in' 1871. * It evidently stands between the other Cladocera and the 
Phyllopoda in many respects, having no slight resemblance to a larval Eu- 
branchipus. 
It occurs in considerable numbers in Peoria Lake, a mere expansion of 
the Illinois River, the depth of which does not exceed eighty feet. Speci- 
mens taken in a small surface net, in June, I 877, were lost in transit, and it 
was not again seen until found in the stomachs of Polyodon , Dorosomo and 
Hyodon. It is not at all certain that this is identical with the European 
species, all the specimens yet studied being too imperfect to decide this point. 
Eurycercus lamellate, Muell. I 
Specimens apparently of this species appear in the stomachs of fishes 
from Crystal Lake, McHenry Co., ( Apeltes , Labidesthes , Fundulus ) and 
also in shovel fishes from Peoria Lake. It is likewise common in ponds in 
McLean Co. 
Bosmino , sp. ? 
This genus belongs to a section of Dapniadae ( Lyncodaphnia ) dis- 
tinguished by the long and strong anterior antennae and by the reduced im- 
portance of the posterior pair. The former are tapering, curved and cylin- 
drical, (containing in our species about 14 slightly spinulose joints, with a 
tuft of bristles on the front of the third) and project from the front of the 
head like a bifid beak. Occurs in myriads in food of shovel fish, in carp, 
buffalo, &c., and in Labidesthes from Crystal Lake. 
Ceriodaphnia angulata , (Say) Forbes. 
Very abundant in central Illinois, (McLean and Rock I. counties) 1 , but 
* Invertebrate Fauna of L. Superior, p. 696. 
