THE PERIDINIALES OF PLYMOUTH SOUND. 191 
the longitudinal groove is inconspicuous. The whole surface is 
covered with longitudinal striz, those on the anterior portion 
being further apart than those posteriorly. Remains of food in 
b- 
ans.) rare 
er ae Oa 
Gy) Z| 
x4 Z) 
ni 
Fie. 6.—Gymnodinium rhomboides Schiitt. x 466 
a side view, ) dorsal view, c ventral and dorsal views of older forms 
containing food masses of Pheocystis, d@ young form containing a 
Thalassiosira, e division. N=nucleus. F=food. 
a ball is often seen in the hind portion of the body. Nucleus 
anterior. The body colourless with no chromatophores. Its food 
consists very often of Pheocystis pouchetii when that flagellate 
is abundant, at other times of diatoms ; remains of Thalassiosira 
and Coscinodiscus were also found inside the body. Division 
takes place in the free state as described and figured by Dogiel. 
