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 setse 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 sette." 



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 CYCLOPID.E. 



The family contains five genera, viz.: Thofellia, Cijclops, Olthona, 

 Lophophorus and Gyclopina; passing, by the genera Misophria and Pseu- 

 do-cyclops, into the Calanidw or marine Gopepoda. 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 antennae seldom longer than the cephalothorax, those of 

 male alike on both sides and modified for the purpose of clasping; 

 posterior antenniTe unbranched (i. e., palpus wanting); palps of mandi- 

 bles and maxillfE usually well developed; foot-jaws mostly less devel- 

 oped than in Ckdanid(e; first four pairs of feet as in Calanidw, 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. 



