7i8 



FRESH-WATER BIOLOGV 



126 (127) 



125 (128) Crest on head and valves. Camptocercus Baird 1843 . . 126 



Form oval; greatly compressed, with crest on head and hack. Valves with angles rounded; 

 small teeth at infero-po steal angle; longitudinally striated. Post-abdomen very long, slender, 

 with numerous marginal denticles and lateral squamae. Claws long, straight, with i basal 

 spine; a series of small denticles terminating in a larger one about the middle of daw; extremely 

 fme teeth thence to apex. Five pairs of feet. 



Post-abdomen vs^ith 15-17 marginal denticles. 



Camptocercus recHrostris Schoedler 1862. 



Head extended or de- 

 pressed. $ without 

 denticles on post-abdo- 

 men. Color yellow- 

 transparent. Length, 

 9, to i.o mm. 



Common everywhere 

 among weeds in mar- 

 gins of lakes, etc. Most 

 of the specimens from 

 the United States are of 

 the variety biserratus. 



Fig. irip. Camptocercus 

 recHrostris. 



0.1 MM. 



127 (126) Post-abdomen with 20-30 marginal denticles. 



Camptocercus macrurus (O. F. Miiller) 1785. 

 Much Uke the preceding. Very rare, but reported from most regions in the United States. 

 Undoubtedly the preceding species has been mistaken for this by some observers. 



128 (125) Crest on valves only. . Kurzia Dybowski and Grochowski 1894. 



This genus is Alonopsis (part) of older authors; Pseudalona Sars, 



Sole American species Kurzia latissima (Kurz) 1874. 



General form subguadrate; 

 greatly compressed; but with only 

 slight crest on back, none on head. 

 Head small, the rostrum reaching 

 not much below middle of valves, 

 though longer than antennules. 

 Post-abdomen long, slender; 

 lower angle usually produced into 

 a lobe; 10-12 marginal denticles. 

 Claws of Camptocercus type. $ 

 Uke 9 ; rostrum shorter; post- 

 abdomen with small denticles; vas 

 deferens opens on ventral (upper) 

 side; strong hook on first foot. 

 Color yellowish, transparent. 

 Length, $, 0.6 mm.; $, 0.4 mm. 



Found in all regions among 

 weeds in pools or lakes. 



Fig. 1120. Kurzia latissima. 



129 (124, 132) Crest on head and valves; post-abdomen broad, without 

 marginal denticles. . . . Acroperus Baird 1843 . . 130 

 Body thin, compressed; crest on head and back. Valves subquadrate, obliquely striated; 

 infero-posteal angle rounded or acute, usually with teeth. Post-abdomen large, compressed; 

 without marginal denticles but with lateral row of squamae. Claws long, straight, with i basal 

 spine and secondary denticles, much as in Camptocercus. Intestine with large intestinal cecum. 

 £ye larger than ocellus. Color yellow-transparent. 



