ENTOMOSTRACA OF MINNESOTA. 217 
depression from the body, very high, slightly arched above, abruptly 
curved below with spines upon the margins. The antenne& are large; 
four-jointed ramus much the longer, with four sete. Labrum with a 
_large process. Post-abdomen much as in Macrothrix laticornis, serrated 
or notched behind. Eye near the beak; pigment fleck small, situated 
below the eye at the base of the antennules. 
The shell is hexagonally reticulate, arched above and angled below; 
ventral margin armed with rigid spines. . Claws ciliate. Length 0.34 
to 0.4 mm. 
Our Macrothrix pauper seems a near approach to this genus; both 
have a strong spine or claw on the first foot which projects beyond 
the shell, but there are many differences. M. pauper is 1.0 mm. long. 
S. serricaudatus Sars (Plate LX VI, Fig. 1) is the only species. 
GENUS DREPANOTHRIX Sars. 
The head separated from the valves by a depression; fornices mod- 
erate; rostrum rather acute, distant from the anterior edge of the 
valves. The form is subrotund; reticulate, with the margins of shell 
fringed below by long movable spines; pigment fleck present; swim- 
ming antenne with three ciliated sete on the four-jointed ramus, the 
three-jointed ramus with its basal joint armed with an unjointed, 
Strong, spinous seta and four ciliated sete on the remaining joints. 
The post-abdomen is broad. Intestine coiled. The male has longer 
antenne and a hook on the first foot. 
Drepanothrix dentata Euren. 
PLATES XLVI, Fia. 9; LIV, Fie. 4; LVI, Fia. 14. 
Acantholcbcris dentata—Euren. 
Drepanothrix setigera—Sars. 
Drepanothrix hamata—Sars. 
* Drepanothrix hamata Norman and Brady. 
This animal is only 0.5 mm. in length. The antennules are later- 
ally curved in the middle and ornamented with notches on the mar- 
gins; the pigment fleck is quadrate and rather large; the post-abdomen 
is truncate at the end, convex behind and ornamented with a series 
of small spines. Shell margins with long spines. 
Birge reports this species from Lake Wingra near Madison, Wis- 
consin. It seems to be repelled by light and is a bottom-loving form. 
Though it swims fairly well, the stiff setz are chiefly used as pushing 
poles. The species has been taken in Denmark, Scandinavia, Eng- 
land and France as well as America. 
