212 F. W. GAMBLE, B,SC. 



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. Provortex affinis (Jensen). 



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

 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 rubrobacillus, n. sp. PI. X, fig. 8 ; PI. XI, 



fig. 12. 



Length '75 mm. Body cylindrical, broadly rounded in front, taper- 

 ing 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 distinct " seam." The free margin is crenulate. 

 Intestine extensive. The gut-cells contains 3 — 8 rods of reddish colour. 

 Whether they are zooxanthellse (as described by v. Graff* in 

 Enterostoma zooxanthellos), or food-remains, is a moot point. Each 

 eye possesses three lenses. The genital aperture is ventral, a short 

 distance in front of the hinder end. A pair of testes lie at the sides of 

 the pharynx ; they lead by wide vasa deferentia into a vesicula seminalis. 

 The penis contains proximally the separate granule-secretion and 

 spermatozoa separated ; distally it is converted into a chitinous copu- 

 latory organ, enclosing an inner muscular layer. The whole is bent 

 into an S-shaped curve. As in Pr. balticus, one portion of the terminal 

 * 'Zool. Anzeiger,' 1886, p. 338. 



