yio 



FRESH-WATER BIOLOGY 



92 (87) No hepatic ceca; setae 



1-1-3 



93 



93 (94) Convolution of intestine in middle of body. Valves crested, with 

 strong tooth on crest Drepanothrix Sars 1861. 



Sole species Drepanothrix dentata (Euren) 1861. 



Valves reticulated; dorsal margin arched, crested, with conspicuous, short, backward- 

 pointing tooth about middle. Antennules broad, flat, twisted, though not so much as in 

 Streblocerus; post-abdomen compressed but not, extended into a thin edge; almost quadrate 

 as seen from side. Margin with 2 rows of small spines, about 20, and with several rows of hairs 

 besides scattered groups; apex truncate, emarginate, with anus in depression. Claws short, 

 broad, crescentic, smooth, or denticulate; 5 pairs of feet. $ much like young 9 ; hook on first 

 foot; post-abdomen without spines; vasa deferentia open in front of claws. Color whitish to 

 yellowish; opaque or transparent. Length, 9> ca - -7 nun.; $ , ca. 0.4 mm. Not commonly 

 collected though widely distributed and probably not very rare in shallow waters of lakes, on 

 bottom or among weeds. Maine, Michigan, Wisconsin, Minnesota, Colorado. 



O.I 



FIG. 1104. Drepanothrix dentata. 



94 (93) 



Convolution of intestine in hind part of body and in post-abdomen. 

 No dorsal tooth Acantholeberis Lilljeborg 1853. 



. . Acantholeberis curvirostris (0. F. Muller) 1776. 



Sole species. 



Form in general angu- 

 lar-oval, not compressed, 

 without crest. Posterior 

 margin of valves rounded 

 over into ventral, both 

 fringed with long, close- 

 set, plumose setae. La- 

 brum with long, slender, 

 conical process. Anten- 

 nules large, flat, somewhat 

 curved, expanded toward 

 apex. Post -abdomen large, 

 moderately broad, not 

 compressed or divided, 

 hairy, with 20 or more 

 small dorsal spines in each 

 row; anus terminal. Claws 

 short, stout, broad, curved, 

 denticulate, and with 2 

 , ., c . . , small basal spines set side 



by side. Six pairs 01 feet. Intestine without ceca, convoluted, the loops lying in great part in 

 post-abdomen. $ resembling young 9 ; antennules with 2 proximal sense-hairs; first foot 

 with small, inconspicuous hook, post-abdomen emarginate dorsally, vasa deferentia open 

 behind claws Color yellow, not transparent. Length, 9 , to 1.8 mm.; $, 0.5-0.7 mm. 



In pools and margins of lakes among weeds, reported especially frequent in Sphagnum bogs. 

 Maine, Wisconsin, Louisiana; probably in all regions of the United States. 



95 (84) Intestine simple 96 



O.5.MM. 



FIG. 1105. Acantholeberis curvirostris. 



