North American FresJi-tvatcr Cyclopidce. 29 



treated, and a more careful inspection of the collections 

 examined would doubtless make evident many interesting 

 facts with regard to the details of distribution. 



I have had, for comparison with our American forms, 

 named European specimens from S. A. Poppe, Prof. G. 0. 

 Sars, and Dr. Otto Schmeil. Those from Poppe were received 

 in 1883 by Dr. S. A. Forbes and represent the following 

 species : Cyclops agilis, helgolandicus, pulchellus, signatus, 

 and strenuus. During the present year Dr. Schmeil has 

 sent specimens of Cyclops fuscus, varicans, leuckarti, albidus, 

 strenuus, serrulatus, viridis, and phaleratus, while Prof. Sars 

 has sent to Dr. Forbes examples of the species of the follow- 

 ing list : Cyclops viridis, nanus, robustus, hyalinus, oithonoides, 

 albidus, fuscus, v emails, macrurus, gigas, leuckarti, insignis, 

 bisetosus, fimbriatus, bicuspidatus, a/ffinis, crassicaudis, phal- 

 eratus, bicolor, scutifer, serrulatus, varicans, dybowskii, l<i- 

 custris, and strenuus. These authoritatively named European 

 specimens have given me the opportunity for comparative 

 studies of American and European Cyclopidse — the first, so 

 far as I am aware, which have been made in America. 



The mere study of American specimens of species first 

 described from European material has not given me, in many 

 cases, the data necessary for a critical judgment of the 

 synonymy of such forms, and I have consequently accepted, 

 as a rule, the determinations of Claus and Schmeil, whose long 

 experience and critical and exhaustive work give to their con- 

 clusions the highest authority. 



The genera and subgenera of Clans ('93a, '93c, '93d) seem 

 to me very convenient subdivisions of this varied genus, and 

 the species of this paper have, so far as possible, been ar- 

 ranged under Claus's groups. I find it necessary, however, 

 to create two new subgenera, Orthocyclpps and Homocyclops, 

 for the two American species C. modestus and ('.titer. The 

 descriptions are incomplete, however, because of the lack of 

 knowledge concerning the males of these two species. 



Certain characters used by some of our American investi- 

 gators for specific distinction have proven unreliable, and a 



