ENTOMOSTliACA OF MINNESOTA. 217 



depression from the body, very high, slightly arched above, abruptly 

 curved below with spines upon the margins. The antennae are large; 

 four-jointed ramus much the longer, with four set?e. Lab rum with a 

 large process. Post- abdomen much as in Macrothrix laticoniis, serrated 

 or notched behind. Eye near the beak; pigment fleck small, situated 

 below the eye at the base of the antenuules. 



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. 



Oar Macrothrix pauper seems !i 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 LXVI, 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 antennae with three ciliated setse on the four-jointed ramus, the 

 three-jointed ramus with its basal joint armed with an unjointed, 

 strong, spinous seta and four ciliated seta? on the remaining joints. 

 The post abdomen is broad. Intestine coiled. The male has longer 

 antennce and a hook on the first foot. 



Drepanothrix dentata Euren. 

 Plates XLVI, Fig. 9; LIV, Fig. 4; LVI, Fig. 14. 



Acanthohhcris dentata — Euren. 

 Drepanothrix seligera — Sars. 

 Drepanothrix hamata — Sars. 



* Drepauotlirix hamata Norman and Brady. 



This animal is only 0.5 mm. in length. The antennules are later- 

 ally curved in the jniddle 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 setiie are chiefly used as pushing 

 poles. The species has been taken in Denmark, Scandinavia, Eng- 

 land and France as well as America. 



