20 THE HANCOCK PACIFIC EXPEDITIONS VOL. 2 



creadiinae. Even the position of the acetabulum is intermediate in 

 some forms such as Paragyliauchen chaetodontis Yamaguti. Mega- 

 solena and Hapladena are definitely associated with such a series 

 but differ from the others in their pecuHar hermaphroditic sac. 

 There results a plausible conclusion that the large distome family 

 Allocreadiidae probably evolved from amphistome ancestors. Or the 

 amphistomes may have evolved from allocreadiid ancestry. 



Type specimens of the new species described in this paper are 

 deposited in the United States National Museum. Paratypes are de- 

 posited at The University of Southern California and in the author's 

 collection. 



