184 MARIE V. LEBOUR. 
In the following list 60 species are recorded. Of these 5 of Gymno- 
dinium, 2 of Sprrodinium, and one of Cochlodinium are new. Twenty-one 
species are, I believe, new records for British seas and 28 are new records 
for the Plymouth area. In addition to those recorded and described 
there are many which I have not been able to identify. Some of these 
are young forms, others collapsed before they could be properly observed, 
and others were distorted. Among these there are probably many new 
species belonging to the Gymnodiniacee. 
The classification adopted is that of Paulsen (1908) in ‘“ Nordisches 
Plankton.” Those marked * are new to Plymouth, those marked N.R. 
are new records for British seas. 
PROROCENTRACE. 
Genus EXuUVIELLA Cienk. 
(1) * Exuviella compressa (Bailey) Ostenfeld. Occasionally in water 
samples in the summer. 
Genus PRoRocENTRUM Khrenberg. 
(2) Prorocentrum nucans Khrenberg. From May to October in the 
water samples, rarely in tow nettings. Commonest in the late 
summer. Its maximum early in September. 
PERIDINIACE. 
Genus Drnopnysis Ehrenberg. 
(3) Dinophysis acuta Khrenberg. Fairly frequent in very fine tow 
nettings, not so common in the water samples. May to October. 
(4) D. acuminata Cl. and L. Common in water samples, usually gets 
through the very fine net. There is a small form of this species 
which occurs more rarely than the type in the spring and early 
summer. 
(5) D. ovum Schiitt. Occasionally in water samples. 
(6) D. rotundatum Cl. and L. Common in water samples. 
(7) D. homunculus Stem v. tripos Gourr. Occurred once only in tow 
nettings, August, 1916. 
Genus GLENODINIUM (Ehrenberg) Stein. 
(8) * Glenodinium bipes Pauls. Common from May to September. 
Abundant in May and June with its maximum in early June. 
This species is so small that it always gets through the very fine 
