NEMERTINES OF PLYMOUTH SOUND. 13 
figure. All the rest were dredged at Stork Point during the same 
month, and were found inside the honeycombed stones with which 
the bottom is there strewn. These specimens were considerably 
larger than the first, the largest being something over 6 cm. in 
length and the smallest between 3 and 4 cm. In all these the 
colour was much paler than in the Cawsand Bay specimen, the red 
lines being represented by buff-coloured lines, and the intermediate 
lines being grey instead of pale pink. In these larger individuals 
the generative organs were ripe. 
This species has not previously been recorded so far north. It 
occurs on the Atlantic shores of France, but is much more common 
in the Mediterranean. A single specimen was found at Guernsey by 
McIntosh. 
Family TETRASTEMMIDAL, Hubrecht. 
Genus THETRASTEMMA, Ehrenberg. 
As has been already remarked, this genus is characterised by the 
very high degree of variation which its members exhibit. It is for 
this reason in many cases extremely difficult to identify a given 
species, or to come to anything like a satisfactory conclusion as to 
the amount and kind of difference which justifies specific separation. 
Such conclusions as are expressed by the recognition of the following 
species are provisional. They are, however, based on a considera- 
tion of the kind and degree of variation exhibited in each case. 
11. T. rtavinum, Ehrenberg. 
This species is very different in appearance from the other 
members of the genus, and, unlike them, exhibits very little variation. 
It is very common, and may be found between tide-marks, but it is 
obtained in larger numbers by dredging in from 5 to 20 fathoms. 
The Duke Rock and Millbay Channel are favorable localities. 
Ripe specimens occur in autumn. 
12. T. porsate, Abildgaard. 
This very common species seems to inhabit every level from 
Joubin’s second zone to his fifth. It was especially common in 
spring and early summer among the Zostera in Cawsand Bay. 
Later in the year, however, it became less common in this locality, 
and late in the autumn it was quite the exception to find a single 
individual there, when a small Terebellid seemed to have taken its 
place. 
