^0 Wisconsin Academy of /Sciences, Arts, and Letters. 



be 0.8 mm. Its back is less arched than that of the female and 

 its ventral margin more convex. The valves gape widely below. 

 The testicle has a thick coat of muscular fibres, both circular and 

 longitudinal, and the vas deferens opens just in front of the anus. 

 The antennules of the male resemble those of the other sex, and 

 the feet of the first pair have a moderately large hook, but no 

 flagellum or a rudimentary one. 

 Cambridge, Mass., 1876. Eare. 



GENUS 2. 

 Maceothrix. Baird, 1843. 



Macrothkix, Baird. Ann. Mag. Nat. Hist., Vol. XI, p. 87, 1843. 



" Liljeborg, Schodler, et al. 



EcHiNisCA, Lieven. 



SPECIES 1. 

 Plate I. Figs. 12-13. 



Macrothrix Eosea. Jurine. 



MoNOCums ROSEUS, Jurine. 1. c, p. 150, Tab. XV. 

 EcHiNiscA ROSEA, Lieven 1. c, p. 31, Tab. VIII, figs. 3-7. 

 Macrothrix " Baird. Brit. Ent., p. 104. 



" Liljeborg. 1. c, p. 47, Tab. IV, figs. 1-2; Tab. V, 



fig. 1. 

 " P. E. Miiller, p. 136, Tab. Ill, figs. 1-4. 



My specimens agree closely with Miiller's description. He 

 .says, however, "Der findes et lidet udviklet Hefteapparat paa 

 samme sted og af samme Bygning som hos Eurycercus." In 

 these specimens it is considerably larger than in Eurycercus, and 

 lies decidedly further back. 



I have seen one male of this species. It is about 0.3 mm. long. 

 The antennules are curved as in the female, and besides, curved 

 outward toward the base, and again inward toward the apex, so 

 as to appear somewhat bow-shaped, as seen from the front. They 

 have five cross-rows of stout, short, black hairs on the outside of 

 each antennuie, and a rather long flagellum near the base. The 

 sense-hairs are short and curved inward. The first feet have a 

 very long hook, stout at the base, its apex projecting from be- 



