REPORT ON L.M.B.C. NEMERTINES. 455 



parallel with the margin of the head than is there indicated, 

 and I have never been able to make out a branch groove 

 uniting the anterior and posterior furrows ; at the angle 

 where the anterior groove bends forward, there is certainly 

 a branch given off, as in A. ^j^t/cAer and other Enoplous 

 Nemertines, but it is quite short and ends abruptly. 



In A. lactifloreus the arrangement is very similar; the 

 grooves being perhaps less conspicuous, and the anterior 

 grooves bending somewhat less forward on the ventral 

 surface so that the mouth-opening, which is in the usual 

 position close behind the tip of the snout, is a little in 

 front of the furrows and not intersected by them. Joubin's 

 figure on p. 132 {5) does not appear to me to be at all an 

 accurate representation of the head of this species. 



Whether the above characters are sufficient to entitle 

 Amphiporus dissimitlans* to specific rank, or whether it 

 should be regarded merely as a variety of A. lactifloreus, 

 it is at any rate a well marked variety which appears to be 

 as strictly confined to the infra-laminarian zone as A. 

 lactifloreus to the littoral. 



It remains to be mentioned that the small Port Erin 

 specimens differ somewhat from the adults seen at 

 Plymouth in respect to two features. In the former the 

 brain is not pink (this may be a juvenile character) and 

 secondly the head is less pointed and more distinctly 

 notched in front than is the case in the Plymouth form. 



Family Tetrastemmid^. 



Tetrastemma flavidum, Ehrenberg. 



This species appears to be well distributed in the 



* It is almost needless to point out that Joubin is in error in assimilating 

 this species with A. pulclier. The two are very distinct, yet the possibility 

 of his having confused them is strongly suggested by the figure and accom- 

 panying description (J, p. 129) referred to above. 



