7o8 



FRESH-WATER BIOLOGY 



83 (23, 76) Antennules of female long, freely movable, usually inserted at 



anterior end of ventral surface of head. Rami of antennae 

 3- and 4-jointed. Intestine simple or convoluted. Hepatic 

 ceca usuaDy wanting. Five or six pairs of feet. 



Family Maceothricidae Norman and Brady . . 84 



Abdominal process usually absent; rarely present {Ilyocryptus). Feet 5 or 6 pai'rs the 

 first two prehensile; the last, if present, rudimentary. Post-abdomen marked off from body, 

 usually large, often bilobed; anus terminal or lateral. Labrura usually with keel or marked 

 projection. Valves often crested. Fornices well developed. . . , , 



The members of this family are so various in form that it is hard to find many common 

 character"^- yet the general appearance is always characteristic. The size and position of the 

 antennules will show the membership of every genus except Ilyocryptus; and there is no trouble 

 in recognizing that genus as belonging to the family. 



84 (95) Intestine convoluted 85 



85 (86) Valves with spine at supero-posteal angle. 



Small hepatic ceca. 



Ophryoxus Sars 1861. 



Sole species Ophryoxus gracilis Sars 1861. 



General form elongated, some- 

 what daphnid. Antennules long, 

 slender, fringed with numerous 

 hairs behind, lateral sense-hair 

 near base; olfactory setae vmequal. 

 Antennae long, weak. Six pairs of 

 feet. Post-abdomen long, taper- 

 ing at apex, anus dorsal, post-anal 

 portion large with numerous short, 

 blunt, cihated spines, the proximal 

 mere elevations bearing fine spi- 

 nules. Claws straight, with (usu- 

 ally) two stout basal spines. In- 

 testine with convolution in middle 

 of body; 2 small hepatic ceca. 

 Antennules of $ longer than 9 I 

 sense-hairs longer. Vasa deferen- 

 tia open on ventral (anterior) side 

 of post-abdomen about middle. 

 Strong hook on first foot. Color transparent, last foot often purple in old 9 • Length, 9 . to 

 2.0 mm.; ^,1.0 mm. , r i_i jji- 



Widely distributed in lakes among weeds. Swims with constant but rather feeble paddhng 

 motion. Spine longer in young than adult. 



86 (85) No such spine 87 



0.1 MM. w._4 



Fig. 1 100. Ophryoxus gracilis. 



87 (92) Hepatic ceca present. 



88 (89) Antennary setae 9 , ; ^ , 1 valves narrowed behmd and 



• 0-0-3 1-1-3 



prolonged into short tube. . Parophryoxus Doolittle 1909. 

 Sole species Parophryoxus tubulatus Doolittle 1909. 



Form elongated oval; narrow crest on head and valves. Head rounded, rostrum well 

 marked; cervical sinus present. Valves thin, transparent; unmarked or faintly reticulated; 

 prolonged behind into a sort of tube, best seen from above; ventral margin with moderate 

 setae. Post-abdomen elongated, triangular; post-anal part long and slender, narrowed toward 

 apex somewhat as in Ophryoxus; bearing a few very small spines. Claws long, rather straight; 

 with 2 basal spines. Antennules cylindrical, slender; with basal sense-hair and three conspicu- 

 ously long olfactory setae. Antennae long, slender; basal joint annulated; setae not conspicu- 

 ously dissimilar. Feet, 6 pairs; the last rudimentary. Eye moderate, with few lenses; ocellus 



