160 TWELFTH ANNUAL REPORT. 



Antennae 11- jointed. 

 Sp. 27. Cyclops diaplianus, Fischer. 



(Plate R. Fig. 12.) 



f Cyclops hieolor, Saks. 



? Cyclops minutus, Glaus, Heller. 



If not the youug of other species, this is a widely distributed 

 form, being known from Russia, Norway, continental Europe, 

 Madeira, and America. The synonyms above given are upon the 

 authority of Re h berg. 



The following description applies to our American form found 

 always in connection with C. thomasi, C. parens, or C. navus. 



Very small, measuring 0.81 mm., setae not included. The thorax 

 is 0.5 mm., the abdomen .31 mm., the stylets .06 mm., the longest 

 caudal seta 0,4 mm., outer median seta .36 mm., the first thoracic 

 segment 0.3 mm., and the egg-sacs sometimes OA mm. The thorax 

 is oval, the first segment being quite large, as in larval cyclops. 

 The antennae rarely reach the end of the first segment aud are 

 either ll-joint'ed or obscurely 12-]ointed; their formula h 

 —^——^— — ~^——. The first joint is very large. 



The second antennae are of rather small size; the maxillipeds are 

 armed as in C. navus. The feet have usually but 2-jointed rami, 

 but in large individuals some of the rami are obscurely 3-jointed. 

 The first foot has the terminal joint of the outer ramus armed with 

 three exterior spines, two terminal setae and three interior setae; 

 the inner branch has one internal spine, a terminal spine and seta 

 and three external setae. The fourth foot has the terminal joint of 

 the outer ramus Avith two external spines, a terminal spine and seta 

 and four internal setae; the inner ramus has one internal spine^ 

 two unequal spines and three internal setae. There is also a series 

 of teeth at the place where the middle joint should appear. The 

 fifth foot consists of a broad, basal segment nearly fused with the 

 abdomen and bearing laterally a long spine; the terminal segment 

 is terete and small, having a single' terminal spine. The caudal 

 stylets are but little longer than the last abdominal segment, which 

 bears teeth below; the sides are parallel, and the lateral seta is f 

 from base. The median setae are long and toward the end show 

 false jointing. The inner seta is longer than the outer which is, 

 however, heavier. Eggs eight to twenty, in narrow elongate sacs. 

 Not uncommon, everywhere. 



