BRITISH MARINE TURBELLARIA. 257 



b. Body distinctly enlarged in front. Tentacles placed well 

 apart at end of first fifth of the body 



Genus Stylochoplana. 

 Species: — St. maculata (two genital apertures). 



2. Mouth subcentral. Main-gut extending in front of (rarely 

 behind) the pharyngeal region. Tentacles absent 



Family Leptoplanidae. 

 a. Body slightly enlarged in front. Marginal eyes absent 



Genus Leptoplana. 

 Species: — L. tremellaris (a "sucker" present between the male 

 and female genital pores). L. Mertensii and L. atomata 

 (doubtful species, see pp. 239-40). 



Section B. — Cotylea. 



3. Anteriorly-placed marginal tentacles usually present. Mouth 

 just behind (rarely in front of) the brain. Penis with a hard stylet 



Family Euryleptidse. 



a. Brightly coloured. Body thickened over the main-gut. Ten- 



tacles large, moveable. Two small cephalic eye-groups. 



Genus ProsthecerjEUS. 

 Species : — Pr. vittatus (body yellow, with longitudinal thin 

 black lines). Pr. argus (dorsal surface orange-coloured ; 

 length up to 10 mm.). 



b. Dorsal surface usually papillose. Tentacles small. Peripheral 



gut-pores to the exterior - - - Genus Cycloporus. 

 Species : — C. papillosus (a median gut-branch over pharyngeal 

 region). 



c. Intestine brightly coloured. Tentacles long. Mouth behind 



brain. Cephalic eye-groups extending far behind brain. 



Genus Eurylepta. 

 Species : — E. comuta (eyes not quite extending back to hinder 

 edge of white pharyngeal region ; body bright red). 



d. Tentacles long. Mouth in front of brain. Pharyngeal sheath 



with a posterior ceecum - - Genus Oligocladus. 

 Species : — 0. sanguinolentus (body whitish, intestine usually 

 carmine ; a short cephalic eye-group). 0. auritus (eyes 

 absent over the brain [Claparede]). 



