ENTOMOSTRACA OF MINNESOTA. 53 



last segment of the thorax is rounded instead of acute, and bears 

 minute bristles. The close agreement of the other parts suggests a 

 local race or variety, but it may be best to retain the name notwith- 

 standing. 



GEKUS PSEUDO-DIAPTOMUS Herrick. 



Resembling Metrida and JDiaptomus; compactly framed; cephalo- 

 thorax six-jointed, last two segments coalescent above; head rounded 

 in front, beaked; eye small; antenuce appearing 22 jointed in both 

 sexes, longer than the thorax; the right male antennae geniculate as in 

 Dkqjtomus; antennules bi-ramose, both rami rather short, inner one 

 seeming but two or three-jointed; mandible ten toothed; maxillipedes 

 well developed; feet all bi-ramose save the last, both rami three- 

 jointed; first feet smaller; fifth feet with inner ramus obsolescent, in 

 the male nearly as in Diapfomus, in the female rather slender, simple, 

 three-jointed; abdomen in the female three-jointed, in the male five- 

 jointed; stylets in the female longer; ovisac single; spermatophore 

 pear-shaped, liable to be mistaken for eggs. 



* Pseiiflo-diaptoimis pelagicus Herrick. 

 Platk I, Figs. 11-17. 

 Herrick, '84 and '87. 



Rather compact; thorax alike in the sexes, antennae short, seeming 

 22-jointed; first foot small, both rami three-jointed; fifth feet in the 

 male with but small rudiments of the inner rami, basal portion heavily 

 armed with short teeth, otherwise almost as in Biaptomus; fifth feet 

 of female slender, alike; abdomen in male very slender, with short 

 stylets armed with five terminal setie and a series of bristles on the 

 inner margins, distal margin of segments of abdomen toothed; a series 

 of spines also ornaments the middle of the first segment below; abdo- 

 men of female short and very spiny, first joint thick, second slender, 

 oblong, third joint short; length of abdomen supplemented by that of 

 the elongated stylets, which are spinulous on the edges; ovisac ovoid, 

 eggs numerous; opening of operculum vulvfe with lateral projecting 

 lips. 



This species is ornamented with irregular markings of brownish 

 color which gives it a strange appearance not observed in any other 

 Copepod. The size is like Temora velox, which the female resembles a 

 little, a resemblance enhanced by the elongated stylets. 



This genus affords an illustration of a "missing link" connecting 

 the fresh- water genus Diaptomus with its fellows of the sea. In most 

 respects the species closely resembles Diaptomus, while in others it ap- 

 proaches Drepanopus, and in still others Euehceta. The entire reduc- 



