yio 



FRESH-WATER BIOLOGY 



92 (87) No hepatic ceca; setae — ^— ^ 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. 0.7 mm.; ^, 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. 



0.1 MM. . I 



Fig. 1 104. Drepanothrix dentata. 



94 (93) Convolution of intestine in hind part of body and in post-abdomen. 



No dorsal tooth Acantholeheris Lilljeborg 1853. 



Sole species Acantholeheris curvirostris {0. F.MiiUer) 1776. 



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 

 small basal spines set side 

 by side. Six pairs of 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 



0.5-MM. » 



Fig. 1105. Acantholeheris curvirostris. 



