712 



FRESH-WATER BIOLOGY 



TOO (107, 116) 



loi (102) 



Antennary setae 



0-0-0-s 



1-1-3 

 Wide crest on dorsal margin of valves. Antennules at apex of 

 head. Post-abdomen bilobed, of moderate size. 



Bunops Birge 1893. 

 Sole American species Bunops serricaudata (Daday) 1888. 



General form rounded, much compressed; 

 high keel on dorsal side. Front of head flat, 

 somewhat kite-shaped, with boss or umbo 

 over eye. Strong triangular keel on la- 

 brum. Valves faintly reticulated, produced 

 behind into rounded projection; ventral 

 margin gaping in front, inflexed behind, 

 fringed with rather long straggUng hairs or 

 weak setae. Antennules with basal sense- 

 hair and two pairs of sense setae near apex; 

 olfactory setae somewhat unequal. Post-ab- 

 domen much like Strcblocerus; bilobed, pre- 

 anal portion flattened, semi-circular, with 7-8 

 notches or teeth on the dorsal margin and 

 3-4 rows of fine hairs; anal portion with fine 

 hairs and 3-4 spines. Color transparent, 

 tinged with yellow. ^ unknown. Length of 

 9 to i.o mm. Maine, Wisconsin; very local 

 in distribution, but not rare when present. 



Fig. 1 108. 



o \ MM. « 



Bunops serricaudata. 



102 (loi) Vertex of head forming sharp angle in front of insertion of anten- 



nules. Dorsal crest of valves absent or small. Post-abdo- 

 men very large, with numerous long spines. 



Ilyocryptus Sars 1861 . . 103 

 ' General form oval-triangular, the head forming the apex of the triangle, while the enorm.ously 

 dilated ventral and posterior edges of the valves round into each other; these have long, close- 

 set fixed setae, usually branched and fringed. Antennules long, free y movable, 2-jomted, 

 basal joint very small, attached to ventral side of head behind vertex; olfactory setae unequal. 

 Antennae short, powerful; basal joint annulated nearly to apex; with long sense setae; motor 

 setae not plumose, smooth, or with sparse hairs. Abdommal process long, tongue-shaped, 

 hairy Post-abdomen large, broad, compressed; anus on side or near apex; many spines on 

 dorsal margin; numerous, long, curved, lateral spines and setae; fine spmulesnear base of 

 claws. Claws long, straight, denticulate, and with 2 slender basal spines. Intestine simple, no 

 ceca, but enlarged near rectum. Six pairs of feet. ^ with larger antennules than 9 , bearing 

 2 sense-hairs; no hook on first foot. ,. , ,. ^, ^- _i 



In most species the old shells are not cast off in molting but overlie the youngest in several 

 layers The species live in mud, creep about among weeds, though they can and do swim; 

 are often greatly loaded with mud and vegetable growths, neariy concealing structure. 



103 (106) Anus opening on dorsal margin of post-abdomen; molting imper- 



fect 104 



104 (105) Eight or more pre-anal spines; antennary setae short. _^ 



Ilyocryptus sordidus (Lieven) 1848. 

 Post-abdomen emarginate 



0.1 MM 



Ilyocryptus sordidus. 



Fig. 1 1 09 

 Not very common but widely distributed in weeds on muddy bottoms 



where anus opens; 8-14 pre- 

 anal marginal spines; lateral 

 post-anal spines about 8-10; 

 marginal row of nvimerous 

 smaller spines. Ocellus 

 nearer base of antennule than 

 eye. Six to eight summer 

 eggs. 



Color red, but often so 

 loaded with debris as to be 

 opaque. Length, 9» ca. i.o 

 mm., $ , 0.42 mm. 



