80 



B. HoLORHYNCHOrOELOMIA. 



Body iisiially short. Prol)osois at least as 

 long as body. Proboscis sheath i-eaches into 

 hinder third of body. 



I'ain. Tetrastemmid.b. 



Four e^'es. Cere]>ral organs in 

 front of lirain. Dioecious or 

 hermaphrodite. 



Genera. Prosoroclimus. 

 Tetrastemma. 



Fam. AMPTiTroKTD.E. 



Numerous eyes. C'erebral organs 

 generally behind brain. As a rule 

 members of this family are con- 

 siderably larger than those of the 

 preceding. 



Genera. Amphiporus. 



Drepan ophorus. 



Fam. Malac()]!Dkllid.e. 



Parasitic in Lamellibranchs. 

 Sucker at posterior end. 

 Genus. MalacohdeUa. 



rv. HETFRONEMERTINI. 



Three muscle layers in body wall, i.e., outer 

 longitudinal, middle circulai, and internal longi- 

 tudinal. Proboscis withoui stylets. ^foiith 

 behind brain. 



Fam. Imi'oliidj-:. 



Without head slits. 

 Genera. Enpolia 



Valenciniri . 

 0.ri/pol/ii. 



