KANSAS ACADEMY OF SCIENCE. 79 



terior edge, with long teeth ; but the first segment, in addition to this, has 

 also on each side one large plumose bristle and two small ones. The position 

 and shape of these bristles strongly remind one of those bristles of the fifth 

 thoracic segment which compose the rudimentary foot. The fourth abdom- 

 inal segment is furnished on the posterior edge with stout, long spines; but 

 on the dorsal surface it has a delta-shaped figure which consists of small 

 teeth. The brauches of the furca are adorned with seven parallel rows of 

 teeth The middle tail-bristles consist, as it were, of three parts — first, the 

 basal, naked; second, the middle, furnished with sparse teeth; and third, 

 the terminal, thickly covered with hair. The largest bristle is equal in 

 length to the whole abdomen ; the other two bristles are very short. On the 

 external edge of the branches of the furca are three spines each. The color 

 is reddish-yellow. 



EXPLANATION OF PLATES. 



[Note.— Separate dissections of the same species were often necessarily drawn under different 

 powers. In fig. 4, plate III, both sides of the third caudal seta should have been represented as webbed. 

 In fig. 2, plate IV, the ridge on the apical joint of the first antenna should have been represented by a 

 double line, as in the two joints preceding.] 



PLATE I. 



Fig. 1. Oyclops elongatus, Cls. . Adult female seen from above. 

 " 2. C. pulchellus, Koch. Swimming-foot of the fourth pair. 



" 3. C. pulchellus, Koch. Apical joint of outer branch of a foot of the second pair. 

 " 4. C. pulchellus, Koch. Apical joint of inner branch of a foot of the second pair. 

 " 5. C. pulchellus, Koch. Apical joint of outer branch of a foot of the third pair. 

 " 6. C. pulchellus, Koch. Apical joint of inner branch of a foot of the third pair. 

 " 7. C. pulchellus, Koch. Apical joint of outer branch of a foot of the first pair. 

 " 8. C. pulchellus, Koch. Apical joint of inner branch of a foot of the first pair. 

 " 9. C. perarmatus, sp. n. Adult female from above. 

 " 10. C. perarmatus, sp. n. First antenna. (This and the following dissections of 



perarmatus are from the female.) 

 " IL C. perarmatus, sp. n. Fifth foot. 

 " 12. C. perarmatus, sp. n. Second antenna. 



" 13. C. perarmatus, sp. n. First abdominal segment, broadened a trifle by mechani- 

 cal pressure, and slightly turned to one side. 

 " 14. C. perarmatus, sp. n. Labrum. 

 " 15. C. perarmatus, sp. n. Second maxilliped. 

 " 16. C. perarmatus, sp. n. First maxilliped. 

 " 17. C perarmatus, sp. n. Maxilla. 

 " 18. C. perarmatus, sp. n. Mandible and palp. 

 " 19. C. elongatus, Cls. Second maxilliped. 

 " 20. C. elongatus, Cls. Second antenna. 

 " 21. C. elongatus, Cls. First antenna of female. 

 " 22. C. elongatus, Cis. First maxilliped. 

 " 23. C. elongatus, Cls. Caudal rami and its furniture. 



