254 F. W. GAMBLE, B.SO. 



Species : — G. hermaphroditus (colourless ; copulatory organ with 

 a straight poison-dart). 



III. Proboscis small, behind the anterior end, its sheath opening 

 on the ventral surface. Granule- and seminal vesicles not 

 separate. Their contents, however, issue by distinct ducts 



Sub-family Hyporhynchinae. 



a. Characters of the sub-family - - Genus Htporhynchus 



Species: — H. armatus (copulatory organ composed of two 



fused chitinous, spiral tubes; pigment not reticular; six 



papillae round the mouth. H. penicillatus (copulatory 



organ composed of two spoon-shaped pieces). 



6. A single genital aperture. Pharynx large, dolioform. A uterus 

 and paired testes present ----- Family Vorticidae. 



I. Germaria small, body-cavity capacious, free-living 



Sub-family Euvorticinae. 

 a. Two germaria and two unbranched vitellaria 



Genus Provobtbx. 

 Species : — P. balticus (copulatory organ with a spirally-curved 

 spur on the margin). P. affinis (copulatory organ slightly 

 bent distally). P. rubrobacillus (with red rods in the gut- 

 cells ; copulatory organ with a finely pointed straight spur 

 to the margin). 



Section C. — Alixeoccela. 



7. An otolith absent - Family Plagiostomidae. 



I. Genital aperture single, ventral, posterior. Mouth anterior. 

 Germaria present. - Sub-family Plagiostominae. 



a. Without tentacles - Genus Plagiostoma. 



Species : — a. With four distinct eyes : PI. sagitta. 



b. With two eyes. 



aa. Mouth terminal or subterminal : PI. dioicum (1 — 5 

 mm. long, yellow, pharynx in front of brain). PI. elongatum 

 (white, pharynx large, when retracted it lies behind the 

 brain). PL ochroleucum (5'5 m.m., pharynx subterminal). 



bb. Pharynx and mouth behind brain. 



