1076 Wisconsin Academy of Sciences, Arts, and Letters. 



Cyclops viridis var. parens Herrick. 



Parens has the second segment of the fifth foot with the 

 spine separated by a joint. The formula for the spines of 

 the terminal segments of the exopodites of the swimming feet 

 is 2, 3, 3, 3, the terminal segment of the endopodite of the 

 fourth foot is armed with a seta. The outer terminal appendage 

 of the furca is a short seta. 



Parens is most common in shallow bodies of water. It does 

 not appear to have a very wide distribution. 



Cyclops viridis var. americanus Marsh. 



Americanus has the furcal rami of varying length, the outer 

 terminal appendage a short seta. (Plate LXXIX, fig. 6.) 



The spine of the second segment of the fifth foot is sep- 

 arated by a joint. The terminal segments of the exopodites 

 of the swimming feet have as the formula of the spines 

 3, 4, 4, 4. The terminal segment of the endopodite of the 

 fourth foot has externally a seta. 



Americanus is the most abundant variety of viridis in 

 American waters, being found almost universally especially 

 in the smaller bodies of water. This is the form which E. B. 

 Forbes calls insectus, reviving the name proposed by S. A. 

 Forbes, but never so described as to make it possible to 

 identify the form. It is evident that in this case americanus 

 has the rights of priority, as it was possible to recognize in- 

 sectus only after the publication by E. B. Forbes in 1897, 

 and he recognizes the identity of the two forms. 



Discussion of viridis. 



The first to recognize clearly the identity of the forms which 

 are here grouped under the common specific name of viridis 

 was E. B. Forbes, and the synonomy which I have adopted 

 does not differ materially from that proposed by him. I 

 agree with him that all the varieties distinguished above 

 merge the one into the other with no clear cut dividing line. 

 This is my impression from the study of my somewhat ex- 

 tensive collections from nearly all sections of North America. 



