BRITISH MARINE TURBBLLARIA. 253 



III. A common genital aperture. Germ-yolk-glands present. Testes 

 rounded. Spermotheca with chitinous appendages 



Sub-family Proxenetrnse. 

 a. Characters of sub-family - - - Genus Proxenetbs. 

 Species : — P. flabellifer (copulatory organ retort-shaped, com- 

 plex; duct of the spermotheca with chitinous teeth). P. 

 cochlear (copulatory organ composed of three spoon-shaped 

 pieces). 



IV. A common genital pore. One germarium. Female accessory 

 organs present. Testes elongate - Sub-family Eumesostominae. 

 a. Copulatory organ traversed throughout its length by the 



ducts of male secretions ... Genus Mesostoma. 

 Species. — M. neapolitanum (copulatory organ funnel-shaped, 

 the margin with a spur ; atrium very large). 



5. The anterior extremity converted into a tactile proboscis, pro- 

 vided with a (usually complex) musculature - Family Proboscidae. 

 I. Proboscis simple, with a sheath or muscle-cone. Short muscle- 

 bundles serve as retractors Sub-family Pseudorhynchinae. 

 d. Characters of sub-family - - Genus Pseudorhynchus. 

 Species: — P. bifidus (hinder extremity bifid; copulatory 

 organ conical, with a screw-like ridge on its outer surface). 



II. Proboscis provided with a sheath opening in front, a muscle- 

 cone, and four long retractors. . Sub-family Acrorhynchinae. 



a. Distinct seminal and granule vesicles, enclosed, however, 



in a common muscular sheath - Genus Acrorhynchus. 

 Species : — A. caledonicus (copulatory organ composed of small 

 chitinous spines). 



b. Duct of granule-vesicle with special chitinous investment 



Genus Macrorhynchus. 

 Species : — M. Naegelii (copulatory organ tubular, with a curved 

 spur longer than the tube). M. crcceus (chitinous tube long, 

 continued directly into the "spur"). M. helgolandicus 

 (a chitinous investment enveloping granule-vesicle and vas 

 deferens ; a poison-dart present). 



c. Two genital pores, the female in front of the male pore. 



Granule-vesicle with chitinous investment Genus Gyrator 



