^^^ TEKTH ANKUAL REPORT 



four.jointed; antennae twenty-four jointed, the right geniculated a« in 

 Centropages {=Ichthyop}iorhia); first pair of feet with the v^mi both 

 three-jomted, like the following; feet of the fifth pair, in the female, 

 hke the preceding, but with a spine of the joint preceding the ter- 

 minal one enlarged and divaricated somewhat as in Centropages; in the 

 male, the right with a two-jointed outer ramus, the terminal joint of 

 which is spined and bears near its base a blunt expression of its inner 

 margin; outer ramus of left foot three -jointed, armed with unequal 

 spines; inner branches smaller, similar, three-jointed; the terminal 

 joint bearing curved spines; ovary and testes as in Dlaptomns, with 

 which the mouth parts agree in the main; eyes medium, confluent; no 

 lower or secondary eye-spots. 



POTOMOICHETOR FUCOSUS, Sp. IIOV. 



(Plate II, Figs. 12-14. Plate III, Figs. 1-8, 18-14.) 



Eather slender, and in size, as well as general appearance, resembling 

 the smaller forms of Diaptomus castor ; antennae rather stout, reaching 

 but little beyond the feet, appendaged as in D. castor, in the male 

 strongly geniculated, but somewhat variously so; the six joints pre- 

 ceding the terminal four are thickened; those preceding the joint or 

 hmge are arcuate on the distal margins; the secondary antennae are 

 about as in Diaptomus; mandibular palp two-branched; the outer three- 

 jointed, the inner two-jointed; the terminal joint of the shorter branch 

 bearing seven setae, of the other four, the proximal joint of the former 

 with three stout spines; the maxilla nearly like Diaptcmus; the pro- 

 cesses have respectively the following numbers of setse : the basal 

 plate eight, the small process at base of posterior branchial appendage 

 one, the appendage itself twelve, terminal portion three groups, first 

 containing nine, the second three and the third four or five, the upper 

 of the anterior processes two and the lower three; fifth feet nearly like 

 the others in size; the right in the male having the outer 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 terminal 

 joint bearing three unequal spines, each of the preceding but one; 

 inner branches similar, three-jointed; terminal joint being short and 

 armed with three short lanceolate setae 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 



