68 KANSAS ACADEMY OF SCIENCE. 



The general ground color is a pale blue-green, and is for the most part hidden 

 by blotches of shining brown. The caudal segments and the alimentary 

 tract are of a beautiful blue. The antenuie, for the most part colorless, have 

 the basal joint brown, the distal portion of the fourth and all of the fifth 

 stained less deeply with the same color, the thirteenth and fourteenth tinged 

 with a still lighter shade of the same, and the apical joint also showing a 

 faint tinge of it. 



Length, exclusive of caudal setse, 1.65-1.71 ram. 



Cyclops tenuicornis, Cls. (PL II, figs. 1-14.) 

 This species is quite common about Cambridge. Agreeing in all its gross 

 structural characters with the European descriptions of tenuicornis, it still 

 seems to differ from the same in some of the finer details of its armature. 

 These details, if actually lacking in European representatives of the species, 

 are suflBcient to characterize the American type as a distinct variety ; but I 

 strongly suspect that they have been overlooked in the European type, and 

 shall therefore merely point them out, leaving the question of identity to be 

 settled by those who command European specimens. 



Either side of the fifth thoracic segment is furnished with three transverse 

 rows of serrulations, of which the posterior one is marginal ; and each of 

 these is continued by a fainter line of more minute serrulations, which ex- 

 tends across the upper side of the segment. The second maxillipeds have, 

 beside the large setse and the small cilia of the anterior and posterior margin, 

 a ring-like cluster of very flexible cilia, which possibly constitute a special 

 sensory organ, on one of the broader sides ( that next the (?) median line of the 

 body) of the basal joint near its distal end, and a smaller and somewhat 

 similar cluster nearer the base of the same joint. A small area at the base 

 of the mandible is thickly studded with sharp points which resemble rap- 

 idly tapering cones. 

 Length, exclusive of caudal setse, 1.74 mm. 



Cyclops viridis, Fischer. (PI. IV, figs. 8-16.) 

 Cambridge. Taken from the pond in the Botanic Garden. 



Cyclops pulchellus, Koch. (PI. I, figs. 2-8) 

 Cambridge. I have seen but a few specimens; these from a rain-pool near 

 the Museum of Comparative Zoology. 



Cyclops Thomasi, Forbes. (PI. Ill, figs. 1-13.) 

 Body slender. Sides of the fourth segment postero-laterally produced into 

 recurved angles, a slight approach to which angulation is seen in the second 

 and third segments. Lateral angles of the fifth, pinched into a slight fold or 

 notch just back of the apex. ( In the male, none of the segments are produced 

 into angles at the sides.) In the first abdominal segment, a lateral indenta- 

 tion marks off* the much-dilated anterior from the tapering posterior portion. 

 The last three abdominal segments do not taper individually, nor scarcely 

 as series. Posterior border of the last abdominal segment set with a fine 



