198 P. W. GAMBLE, B.SC. 



Habitat. — This is a typical deep-water (8 — 20 fms.) Turbellarian. 

 Only once have I taken it between tide-marks. When dredge-material 

 is placed in sea water, dark oval specks (the present species) are often 

 seen swimming actively at the surface. In a few hours they descend, 

 and reappear only when the water begins to foul. Plymouth (F. W. G.). 



Distribution. — Naples (Schmidt and v. Graff), Messina (Graff), 

 Sebastopol (Uljanin). 



13. Promesostoma lenticulatum (Schmidt [28]). PI. X, fig. 6 ; 

 PI, XI, figs. 13, 17, 

 Length '65 — "7 mm. (i.e. half that of Schmidt's specimen). Body 

 broadly truncate and slightly convex in front, the antero-lateral 

 margins produced slightly outwards. Behind these it becomes 

 narrower, forming a " neck ; " it then widens towards the middle, 

 diminishing again to the posterior end. The general shape is, in fact, 

 similar to Jensenia (see Jensen [49], pi. iii, figs. 1, 2), but more 

 elongate. Colour to the naked eye scarlet ; this is due to the contents 

 of the extensive gut. Movements extremely active. Epidermis very 

 transparent. Rhabdites few, scattered. Pharynx placed slightly in 

 front of the middle of the ventral surface. Intestine large, corres- 

 ponding to the shape of the body. The eyes are provided with a 

 large conspicuous lens, which is easily detached from the pigment- 

 cup. The genital aperture is a short distance behind the pharynx. 

 The testes have the usual relations, and lead at their posterior ends 

 into the vasa deferentia, which unite to open into the base of a most 

 remarkable copulatory organ. This is cylindrical at its proximal end, 

 provided distally with a series of triangular chitinous plates ranged 

 round the terminal slit. The whole resembles the tool known as a 

 " rose-bit " or " counter-sink," and used for embedding the heads of 

 screws in wood or metal. The base of this organ is divided into 

 spermatic and granule portions. The germaria are placed posteriorly. 

 On one side the germarium was normal ; on the other it was composed 

 of lenticular masses, with difficulty separable optically from one 

 another. The paired yolk-glands occupy the greater part of the sides 

 of the body. 



Habitat. — Two specimens from a tide-pool among corallines, Port 

 Erin, Isle of Man (F. W. G.). 



