BRITISH MARINE TURBELLARIA. 519 



brain). PL elongatum (white, pharynx large, when 

 retracted it lies behind the brain). PI. ochroleucum 

 {5*5 mm., pharynx subterminal). 



BB. Pharynx and mouth behind brain. 



a. Epidermis without pigment : PL Girardi 

 (colourless, 2 reniforra eyes). PL siphonopho- 

 rum (with median longitudinal band of black re- 

 ticular pigment) . PLpseudomaculatum (violet pig- 

 ment between the eyes, without distinct lateral 

 grooves). PL vittatum (pigment variable, usually 

 in the form of three transverse bands). 



/3. Epidermis pigmented : PL sulphureum 

 (epidermis with yellow rods), PL Koreni (trans- 

 verse band of parenchymatous pigment). PL 

 caudatum (rhabdites few, head marked oflF by 

 lateral grooves). 

 b. With two tentacles at the anterior end 



Genus Vorticeros. 

 Species: — V. auriculatum (violet reticular pigment 

 over the greater part of dorsal surface). V. luteum 

 (pigment uniformly yellow). 



II. A single posteriorly-placed genital aperture. Two 

 germaria and two distinct vitellaria. Pharynx directed 

 backwards . . . Sub-family Allostominae. 



a. Without a circular ciliated groove on the head 



Genus Enterostoma. 



Species: — E. austriacum (four eyes; pigment in 



rounded yellow masses). E.fingalianum (pigment 



absent, colour due to food). E. caecum (eyes 



absent). 



b. With a circular ciliated groove at the level of the 



brain ..... Genus Allostoma. 

 Species: — A. pallidum (adults 2 — 3 mm. long; 

 granular mucus-rods [pseudo-rhabdites] in the 

 epidermis). 



