BRITISH MAEINE TURBELLAEIA. 477 



the spherical pharynx and mouth. The remaining anatomy 

 has been investigated by Jensen (49), whose figures (pi. v, 

 figs. 1 — 8) are highly characteristic. 



Habitat. — On the inner side of the Breakwater, and else- 

 where among algee between tide-marks, Plymouth Sound 

 (F. W. G.) ; a specimen at Millport (v. Graff). 



Distribution. — Bergen (Jensen). 



39. ? Plagiostoma siphonophorum (O. Schmidt, 28). 



Length '9 mm. Body elongate, truncate in front with 

 rounded angles, tapering posteriorly. Along the mid-dorsal 

 line is a narrow band of reticular black pigment, which 

 expands laterally behind the eyes and extends between and 

 beyond them anteriorly. Bohmig has shown (57, pp. 208-9) 

 that this pigment is present in the gut-cells and not in the 

 parenchyma. The mouth lies beneath the brain. The 

 pharynx, when extended through the mouth, is narrow, 

 cylindrical, expanded slightly at the distal end. My observa- 

 tions on the genital organs are incomplete. The penis is 

 pyriform, armed at its base with small chitinous spines. 



Habitat.— In 15 to 18 fms., Plymouth Sound (F. W. G.). 



Distribution. — Lesina (Schmidt), Trieste (v. Graff, Boh- 

 mig). 



As ripe sperm was not seen, this species remains doubtful. 

 But other characters agree with PI. siphonophorum, so I 

 refer my specimen to this form. 



40. Plagiostoma Girardi (Schmidt, 32). 



Length 1-75 — 2 mm. Southern examples range up to 

 3 ram. Body slightly depressed, rounded in front, tapering 

 behind, broadest in the middle, v. Graff's figure (' Monogr.,' 

 pi. xviii, fig. 12) does not represent the form well, whereas, as 

 Bohmig has remarked, the figure of PI. ochroleucum would 



