244 



THE AMERICAN NATURALIST 



[Vol. XL 



Fifth foot (Fig. 5) uniramose, three 

 segmented. First segment about as broad 

 as long, slightly tapering toward its free 

 end; armed at outer distal angle with a 

 slender spine. Second segment two thirds 

 as broad as long, sHghtly longer than pre- 

 ceding segment, armed on distal end with 

 a sharp spine at outer angle. Third seg- 

 mont half as broad as long and one third 

 Idiifjcr than second segment, armed on 

 iniHT margin with three strong acute 



side ; at the apex with three strong spines 

 (middle one denticulate) the innermost of 

 which is longest, being one third the 

 length of the segment; on the outer mar- 

 gin at the distal third armed with a small 



155. ■ ' ■ Length of female 2.04-2.81 mm. 



Genus Diaptomi s Westwood 



? Diaptomus ashlandi Marsli.— A sinirlc specinuMi, doubtfully 

 identified as heloiifjinir to this species, was taken at Cambridge, 

 May 1 !)():.. 



Diaptomus leptopus Forho. This >].,ci(s \va> common from 

 the middle of Mav to the muhWv of ( )ct.)l>cr. Localities: Cam- 

 bridge. Medfonl. Wellesley. 



Diaptomus sanguineus Forbes. — Collected at Welleslev and 

 Medfonl in April and May. 



Diaptomus pygmaeus n. sp. 



Fijrs. 1-3 



