ENTOMOSTRACA OF MINNESOTA. 87 
branch but two-jointed by the coalescence of the two outer to form an 
arcuate and deformed appendage, armed at the end with three stout 
equal spines; corresponding branch of left foot three-jointed; the ter- 
minal joint bearing three unequal spines, each of the preceding joints 
only one; inner branches similar, three jointed; terminal joint being 
short and armed with three short lanceolate sete and three longer 
ones, two of which are curved so as to be slightly prehensile; fifth foot 
of female with both rami three jointed; inner ramus much smaller; 
antepenult segment of the outer ramus extending into a large lanceo- 
late process; ovisac long-ellipsoidal or spherical, reaching nearly to 
the end of the caudal setz.”’ 
Professor Lilljeborg finds this species in Oregon, and as we have 
collected it in Alabama it may be regarded as ubiquitous in North 
America in suitable stations. 
FAMILY CYCLOPIDE. 
The family contains five genera, viz.: Thorellia, Cyclops, Oithona, 
Lophophorus and Cyclopina; passing, by the genera Misophria and Pseu- 
do-cyclops, into the Calanide or marine Copepoda. The affinities of 
these little known genera need further study, as they are very inter- 
esting, the question being still open in how far the cyclopoid forms 
are altered by adaptation to saline habitat, if such an adaptation 
takes place at all. 
Cephalothorax ovate and usually much more robust than the abdo- 
men; anterior antenn seldom longer than the cephalothorax, those of 
male alike on both sides and modified for the purpose of clasping; 
posterior antenne unbranched (i. e., palpus wanting); palps of mandi- 
bles and maxille usually well developed; foot-jaws mostly less devel- 
oped than in Calanide; first four pairs of feet as in Calanide, fifth pair 
rudimentary, alike in both sexes, and usually one- or two-jointed; 
ovisacs two. 
The circulatory system of this family is partly lacunal and has 
been thought to be entirely so in the genus Cyclops. Closer observa- 
tion, however, shows that there is something like an imperfect central 
organ at the point occupied by the heart of higher Copepoda. This 
was figured in my previous report, Plate V, Fig. 1, but no mention 
was made of the discovery. It has since been verified. The appa- 
ratus referred to is a modification of that described under Canthocamp- 
tus. In the second thoracic segment there is a set of swaying mem- 
branes which constitute a valvular apparatus, chiefly moved by the 
action of the stomach. 
The following analytical key from Brady will serve to differentiate 
the genera. 
