41 



Phagoa ata arenophila Carpenter, 1969a 



b 0.5 mm 



Fig. 42 after Kenk (1970a). 



Up to 22 mm long and 2 mm wide. Head truncated, with straight, convex, 

 or slightly wavy frontal margin. Lateral edges rounded, protruding 

 laterally to some extent so that there is a narrowing or neck behind 

 them, rather conspicuous in some populations. Eyes normally two, their 

 distance from each other being about 1/3 the width of the head, the 

 distance of each eye from the lateral margin smaller than from the fron- 

 tal margin. Dorsal side gray to black, ventral side lighter. Dis- 

 tinguishable from other similar species only by anatomical characters. 

 Testes predominantly ventral, extending posteriorly to almost the tail 

 end of the body. Penis consists of a weakly muscular bulb and a short, 

 rather plump papilla the tip of which is drawn out into a flattened lobe. 

 Sperm ducts enter the bulb anteroventrally and unite within the bulb to 

 a short common vas deferens. This opens into a small cavity, the seminal 

 vesicle, from which a narrow ejaculatory duct proceeds in a postero- 

 ventral direction to open on the ventral side of the papilla. The common 

 oviduct opens into the posterodorsal part of the male atrium, the duct of 

 the copulatory bursa ends very close to the gonopore. The most outstand- 

 ing specific characteristics are the lobular tip of the penis papilla, the 

 configuration of the penial lumen, and the postpharyngeal extension of the 

 testicular zone. In cold mountain springs and streams in the Rocky 

 Mountains and the Sierra Nevada. Literature: Carpenter C1969a) , Kenk 

 (1970a). 



39 



