THE CRUSTACEA OF NEW JERSEY. 59 



of valves. Antennre short. Eye larger than pigment fleck. Abdo- 

 men flattened, excavated in male. Intestine with no anterior 

 cjeca, doubly convoluted, with an anal caecum. 



These animals are minute round creatures appearing like mov- 

 ing pin-heads as they wander about with a waveriug or rolling 

 motion. They usually live on vegetation, or slime, which occurs 

 in the bottoms of small, quiet pools. In bright sunlight, which 

 they seem to prefer, they sometimes occur in immense numbers 

 near the surface. The males have been found but rarely. These 

 animals are, in fact, among the most minute of all our Ento- 

 mostraca. 



Key to the species. 



a. Post-abdomen armed with eight or nine teeth. sph.Ericus 



aa. Post-abdomen armed with a double row of twelve teeth. bicornutus 



Chydorus sphasricus (Miiller). 



Pl.^te 7. 



Lynceus sphccricns Miiller, Zool. Dan. Prodrom., 1776, p. 199. Denmark. 

 ' Herrick and Turner, Geol. N. Hist. Surv., Zool. Ser., II, 1895, p. 261, 



PI. 64, figs. 4, 7, 8, 10. "Whole circumpolar land area." 

 Chydorus sphccricits, Fellows, Proc. Amer. Soc. Micros., IX, 1885, p. 176. 



Lake Chautauqua, N. Y. ; 1. c, X, 1887, p. 249 same material). 

 M. J. Rathbun, Occas. Papers Boston Soc. N. Hist., VII, No. 5, 1905, 



p. 113. '"Common." 



Description. — Body in profile nearly spherical, and as viewed 

 from above broadly oval, though young rather squared or trun- 

 cate behind. Head not distinct from rest of body. Eye small, 

 inconspicuous. Beak moderately long, blunt in male. Anten- 

 nules moderate, very large in male, with nearly median curved 

 flagellum on anterior edge. Pigment spot nearly large as eye. 

 Shell reticulate, each one polygonal in form. Post-abdomen 

 broad, short, end rounded and furnished with eight or nine sharp 

 teeth. Color of body dull or pale brownish, generally. Length 

 0.5 mm. 



Remarks. — I first discovered this species in New Jersey in pools 

 of fresh water about South Dennis, in Cape May County, on 



