BRITISH MARINE TURBELLARTA. 469 



latory organ. This organ is slightly variable in shape, and 

 consists of a wide, cylindrical, tubular basal portion, open- 

 ing through a narrow transverse slit, one edge of which is 

 continued parallel to the axis of the cylinder, and then bends 

 sharply at right angles. Germ- and yolk -glands lateral; near 

 their point of union is a curved sperm otheca. 



Habitat. — This very active tiny animal occurred abundantly 

 among Laminaria and also in brackish water at Millport 

 (v. Graff) . Abundant in tide-pools. Port Erin, Isle of Man ; 

 less commonly at Plymouth (F. W. G.). 



Distribution. — West coast of Greenland (Levinsen), West 

 Norway (Jensen), Copenhagen (Fabricius, 9). 



29. PuovoRTEX AFFiNis ( Jcusen) . 



Length -6 mm. Body stouter than in Pr. balticus, taper- 

 ing posteriorly from the anterior third. Pharynx not so 

 moveable as in the previous species. It is, however, in the 

 form of the copulatory organ that these species are most 

 easily and certainly distinguished. This is elongate, funnel- 

 shaped, the terminal part of the duct bending at an obtuse angle 

 with the proximal portion. Opposite this angle is a triangular 

 plate projecting outwards from the surface of the duct. 



Habitat.— Along with Pr. balticus, Millport (v. Graff); 

 Plymouth, along with Monoporus rubropunctatus (F. 

 W. G.). 



Distribution. — Copenhagen (Fabricius), Bergen (Jensen). 



30. Provortex bubrobacillus, n. sp. PI. XXXIX, fig. 8; PI. 

 XL, fig. 12. 



Length '75 mm. Body cylindrical, broadly rounded in 

 front, tapering slightly posteriorly. Colour mottled brown 

 to the naked eye. The effect is due to numerous rods of 

 doubtful nature in the interior of the gut-cells. They were 

 present in all individuals examined. Pharynx without a dis- 

 tinct "seam." The free margin is crenulate. Intestine 

 extensive. The gut-cells containS— 8 rods of reddish colour. 



