308 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



93. Prostoma rubrum (Leidy), 1850 



Emea rubra Leidy, 1850; Stichostemma ascensoriatum Montgomery, 

 1896; Child, 1901 ; S. rubrum Coe, 1918. 



Habitat. Creeps on living and dead leaves in pools, ponds, and quiet 

 streams; feeds on minute worms, insects, Crustacea, and unicellular 

 organisms in great variety. In turn, devoured by larger vi^orais, insects, 

 and Crustacea. 



Distribution. Widely distributed throughout the United States from 

 Nevv^ England to Georgia on the Atlantic seaboard and westvi^ard to 

 Washington and California. 



Reproduction. Hermaphroditic; eggs and spermatozoa develop in 

 each gonad ; spermatozoa may mature first but are retained in gonad until 

 ovulation occurs. Hence self-fertilization is the rule, although cross 

 fertilization may ensue when two ovulating individuals are closely asso- 

 ciated. 



Suborder POLYSTYLIFERA 



Key to Tribes 



1. Body adapted for burrowing or creeping; not specialized for 

 pelagic life; proboscis sheath provided with caecal appendages 

 Errantia 



1. Bathypelagic; body adapted for free swimming far beneath the 



surface of the oceans; proboscis sheath without appendages . Pelagica 



Tribe 1. Errantia 

 Only a single family, Drepanophoridae, has been found on the Pacific 

 coast. This appears to be represented by a single genus. 



Genus DREPANOPHORUS Hubrecht 



Two species on the Pacific coast have been identified as belonging to 

 this genus. 



Key to Pacific Coast Species 



1. Body relatively long and ribbonlike; dorsal surface yellowish 



brown to dark brown, with lighter or whitish lateral borders . crassus 



1. Body relatively short and broad ; dorsal surface dull red, reddish 



brown or orange, thickly sprinkled with fine brownish dots . ritteri 



