THE PERIDINIALES OF PLYMOUTH SOUND. 185 
net. It is exceedingly active and lives many hours in a 
bottle of sea-water. 
Genus ProroceRAtTiuM Bergh. 
(9) * Protoceratium reticulatum (Cl. and L.). Occurs fairly commonly 
in water samples from May to September, commonest in August. 
Genus GONIAULAX Diesing. 
(10) * Goniaulax triacantha Jorgensen. Rare, in water samples, May to 
September. 
(11) G. polygramma Stein. Rare, in water samples, May to Sep- 
tember. 
(12) G. spinifera (Cl. and L.). This is the commonest species of Goniaulaz. 
May to September. 
(13) N.R. G. scrippse Kofoid. Occasionally in the water samples, 
July to September. 
(14) G. polyedra Stein. Occasionally in water samples, May to Sep- 
tember. 
Genus AMyLAx Meunier. 
(15) N.R. Amylax lata Meunier. Occurred a few times singly. Slightly 
smaller than the type. 
Genus DipLopsauis Bergh. 
(16) Diplopsalis lenticula Bergh. Fairly common in very fine tow 
nettings and in water samples. May to September. 
(17) N.R. D. pillula Ostf. This minute species is abundant in June in 
the water samples, very often with Glenodinium bipes. 
Genus PERIDINIUM Ehrenberg. 
Sub-genus PROTOPERIDINIUM Bergh. 
(18) Peridinium orbiculare Paulsen. Occurs rarely in the water 
samples. 
(19) * P. cerasus Paulsen. This little species is one of the commonest 
and easily recognised. Occurs fairly frequently but never in 
large quantities in the water samples. 
(20, * P. roseum Paulsen. Very like the last species but larger and 
flatter. Occurs rarely in the water samples. 
