FJtESH WATER CYCLOPID.E AND CALANIDJC. 15 



apicalium rami interioris pedum quarti paris interior altero cluplo 

 longior," and in the synopsis* he states with reference to the 

 external branch, tl intus setis 3, extus aculeis 3 instructus." I 

 give drawings of the fourth foot of a Wanstead Park specimen, 

 from which it will be seen that the last joint of the outer branch 

 possesses only two marginal spines. Dr. Clans gives the length 

 of his species as 2 millimetres — a discrepancy perhaps of no great 

 moment : in other respects his description is applicable to the 

 specimens here described. Mr. Herrick, in his elaborate memoir 

 on the Crustacea of Minnesota, includes under the term Cyclops 

 pulehellus , Koch, several forms which have been described by 

 various authors as distinct species : these are C. bicuspidatus, 

 Claus ; C. Thomasi, Forbes ; C. navus, Herrick ; C bisetosus, 

 Eehberg ; C. bicuspidatus, Pars, and (?) C. insectus, Forbes. The 

 species appears to be generally distributed, though by no means 

 very common, — having been noted by Sars in Norway, Eehberg 

 and Claus in Germany, Dr Anton Fric in Eohemia, and Forbes 

 and Herrick in the United States of America. It appears to 

 differ in certain minor characters from all of the forms described 

 by Forbes and Herrick, while agreeing with Sars' description of 

 C. bicuspidatus in the more important points, excepting the 

 spinous armature of the swimming feet. It would seem impos- 

 sible, without actual comparison of authentic specimens of these 

 various forms, to come to any certain conclusion as to their 

 specific distinctness. 



8. Cyclops Thomasi, Forbes (PL VI., figs. 1-4). 



1882. Cyclops Thomasi, Forbes (38), p. 640, pi. IX , figs. 10, 



11, 16. 



1883. ,, ,, Cragin (40), p. 3, pi. III., figs. 1-13. 



1884. ,, ,, Herrick(41),p.l51,pl.U,figs.4,5,7,8. 



Female. — Eody obtusely rounded in front, abdomen much nar- 

 rower than the cephalothorax ; none of the segments are very 

 prominent laterally, but the posterior angles are much produced 

 backwards, forming sharp cusps, the segments rapidly decreasing 



* The specific name appears in the synopsis as bispinosus, but the reference is 

 apparently to bieuspidatus. 



80 



