REPOET ON L.M.B.C. NEMERTINES. 461 



the central apparatus of some of the Port Erin specimens 

 of Prosorhochmus. The examination of more specimens 

 is desirable before forming any conclusion as to their 

 relation with other forms. 



Tetrastemma vermicidatum (Quatrf.), M'Intosh. 



This usually abundaiit species does not seem to be at 

 all common in the district. I have only met with three 

 specimens. Two of a deep flesh-colour — the larger a 

 mature female 12 mm. long — were found in weeds from 

 between tide-marks at Perwick, the third came from the 

 Clets in Calf Sound and was of a rich apricot-yellow 

 colour. In all three the head w^as fairly oval in outline, 

 a point which serves in some degree to distinguish this 

 from closely allied species, but in none was there a trace 

 of the dorsal white line which Joubin considers its most 

 reliable character. 



Tetrastemma melanoceplialitm (Johnst.), M'Intosh. 

 T. vielanocephalum, Hubrecht. 

 T. coronatum, Hubrecht. 



This species is fairly abundant and well distributed in 

 the district, inhabitino; the weeds between tide-marks and 

 also the shell and coralline ground in 15 to 20 fathoms. 

 At Easter, 1894, a few large greenish specimens were 

 found (up to 3j cm. long), but the numerous examples 

 collected in June and July, 1895, were all immature, 

 averaging only about 1 cm. in length. They presented a 

 considerable range of colour-variation, different shades of 

 flesh and salmon-colour and of yellow from pale greenish- 

 yellow to deep apricot being noted as the ground colour. 



A median dorsal white line was present in many 

 specimens, and the majority had 'more or less opaque 

 white on the head in front of, and immediately posterior 

 to, the patch of dark pigment. The latter was reddish 

 brown or chocolate in colour and very variable in shape. 



