ENTOMOSTRACA OF MINNESOTA. 



95 



* Cyclops brevispinosiis Herrick. 1884. 

 Plates XXni, Figs. 1-4; XX[V, Figs. 7-12. 



This species may be regarded as the pelagic represeatative of 

 G. parens. la the original description the following differences were 

 noted. The form is more slender and the stylets are greatly elongated, 

 the outer caudal seta is reduced to a short ciliate spine, and the fourth 

 foot is differently armed and the receptaculum is somewhat different 

 in form. 



Marsh says that one might infer from my statement that the arma- 

 ture of the swimming feet is the same as in C. parous, but how this 

 could be possible in the face of the plain statement of difference and 

 figure of the fourth foot it is hard to see. 



The first segment of the compact thorax is half its entire length 

 and the antennae are rather shorter. The abdomen is rather slender 

 and tapering. The stylets are 4.5 times as long as wide, and the 

 small lateral seta is more than two-thirds its length from the base. 

 The outer terminal seta is transformed into a very short stout serrate 

 spine, shorter than the inner seta and one-third as long as the stylets. 

 The outer median seta is less than three times as long as the stylet and 

 is naked for more than half its length, when it is suddenly narrowed 

 and very closely pectinate to the end. The inner median seta is 

 almost exactly three times as long as the stylet, and is sparsely pecti- 

 nate for its middle third and closely so for its apical third. 



The armature of the feet is as follows: 



Outer ramus 



Outer ramus 



Outer ramus 



Outer ramus 



ex. 

 ap. 

 in. 



ex. 

 ap. 

 in. 



ex. 

 ap. 

 in. 



ex. 

 ap. 



First Foot. 

 3 spines. ( ex. 



2 setse. Inner ramus \ ap. 



2 seise. ( in. 



Second Foot 

 3 spines. 

 1 spine, 1 seta. 

 3 setse. 



Inner ramus 



Third Foot. 

 3 spines. 



1 spine, 1 set». Inner ramus 



3 sefse. 



Fourth Foot. 

 3 spines. 



1 spine, 1 seta. Inner ramus 



3 sette. 



ex. 

 ap. 

 in. 



1 seta. 



1 spine, 1 seta. 



3 setse. 



1 seta. 



1 spine, 1 seta. 



3 setaj. 



ex. 1 spine, 

 ap. 2 spines, 

 in. 3 selaj. 



ex. 1 spine, 

 ap. 2 spines, 

 in. 2 seta;. 



The basal segment of the fifth foot is little expanded and bears one 

 seta while the short second joint has an apical seta and a small lateral 



external spine. Formula for antennie, — — ^ — ^ ^^~^^ — ^^ — — 



Antennules rather short. Length 1.0 mm. Marsh suggests that this 

 may be a pelagic form of C. viridis var. Americaniis, in which case 

 C. parens would become a variety of the same species. 



