ENTOMOSTRACA OF MINNESOTA. 53 
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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. 
GENUS PSEUDO-DIAPTOMUS Herrick. 
Resembling Metrida and Diaptomus; compactly framed; cephalo- 
thorax six-jointed, last two segments coalescent above; head ‘rounded 
in front, beaked; eye small; antenne appearing 22-jointed in both 
sexes, longer than the thorax; the right male antenne geniculate as in 
Diaptomus; 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 Diaptomus, 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. 
* Pseudo-diaptomus pelagicus Herrick. 
PLATE I, Fias. 11-17. 
Herrick, ’84 and ’87. 
Rather compact; thorax alike in the sexes, antenne 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 Diaptomus; fifth feet 
of female slender, alike; abdomen in male very slender, with short 
stylets armed with five terminal sete 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 vulvz 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 Hucheta. The entire reduc- 
