20 PROCEEDINGS OF THE ACADEMY OF [Jan., 



THE DISTRIBUTION OF THE GENUS CYCLOPS IN THE VICINITY OF 

 HAVERFORD, PENNSYLVANIA. 



BY REYNOLD A. SPAETH. 



The original purpose of this paper was, after the notes and obser- 

 vations of two years had been collected, to prove that by a careful 

 and regular study of the water from a single locality, many of the 

 forms of the Cydo'pidce which are now considered rare would be 

 found to be quite abundant, at least at certain seasons of the year. 

 Owing to unforeseen circumstances, this purpose had to be abandoned 

 in part, and although all the forms recorded in this paper have been 

 taken from a single small pond in the vicinity of Haverford College, 

 the records of monthly abundance or rarity of the different species 

 are not complete. Certain species, notably C. varicans, C. fimhriatus 

 var. poppei, and C. phaleratus, appear far more abundantly in the 

 spring from the middle of March to the end of May. C. prasinus 

 I have found in the greatest numbers in September and early October 

 collections. C. alhidus, C. viridis var. insectus, and C. serrulatus do 

 not vary so noticeably in the collections, while C. fuscus is the most 

 unvarying species of the genus, a few being found in the water taken 

 the year round. 



In his paper of '97, E. B. Forbes has made a most excellent revis- 

 ional study of the North American Cydopidce. His work has sim- 

 plified investigation for all future workers in this field, and his very 

 careful and excellent observations can hardly be overestimated. 

 I have followed his system of subgenera to avoid confusion. 



Cragin's paper of '83 has scarcely received due credit from the 

 investigators who have followed him. His drawings show con- 

 siderable accuracy of detail and very few of the important structural 

 features have escaped his notice. 



Marsh's work has been rather more of a plankton study than one 

 of in.dividual structure. Brewer's paper of '98 lays considerable 

 emphasis on feet-armature, which is now generally considered a 

 variable feature and not a reliable character for specific distinction. 



Miss Byrnes' recent paper of '09 is somewhat confusing. Rather 

 unfortunately she has reverted to Herrick's varietal names of C. 

 ^ignatus, has credited Forbes with both C. bicuspidatus Claus and 

 C- serrulatus Fischer in her list of species studied, and has confused 



