478 F. W. GAMBLE. 



do so. Colour white. Movements sluggish. Rhabdites 

 abundant over the surface. Pharynx small, opening through 

 the mouth behind the brain. Eyes two, reniform, with lenses. 

 According to Bohmig (57, p. 355), the "ciliated furrow '' 

 forms a transverse groove in front of the mouth, and does 

 not correspond to a slight constriction which occurs behind 

 the eyes. For the genital organs the accounts of v. Graff 

 and Bohmig may be consulted. The spermatozoa consist 

 of atnidrib, bearing broad triangular hyaline membranes, 

 and terminating in a short anterior and a longer posterior 

 flagellum. 



Habitat. — Not uncommon 6 — 15 fms., Plymouth Sound 

 (F.W. G.j. 



Distribution. — Naples (v. Graff), where it is the most 

 abundant Rhabdocoele ; Trieste (v. Graff and Bohmig) ; 

 Messina (v. Graff). 



41. Plagiostoma ochroleucum, v. Graff. 



Length 5*5 mm. Colour whitish yellow. Mouth sub- 

 terminal. Pharynx very small, beneath and in front of the 

 brain. Remaining anatomy similar to PI. Girardi. 



Habitat. — 1^ fms. among Laminaria, Millport (v. Graff). 



Genus 18.— Vorttceros, O. Schmidt (28), 1852. 



Plagiostominse with two tentacles at the anterior 

 end. 



42. VoRTicEROs auriculatum (O. F. Miiller, 4). 



Length 1*5 mm. Body produced anteriorly into a pair of 

 long tentacles. Behind the eyes it is slightly constricted, and 

 then expands towards the middle, tapering behind to a fine 

 point. The tentacles are not often seen fully extended. At 

 the slightest alarm they can be completely withdrawn, and the 



