192 IHE AMERICAN NATURALIST. 
I have called the dinoflagellate with which these notes are 
chiefly concerned Gonyaulax, because in the first place it 
approaches that genus very closely, and in the second place 
such a small amount of the literature of the group is accessible 
to me that I do not feel warranted in erecting a new genus 
for it. It differs from Gonyaulax as described in Engler and 
Prantl's Die natürliche Pflanzenfamilien only in that in the 
anterior moiety of the cuirass there are six intermediate plates 
instead of five, and four end plates instead of three.! It may be 
described as follows (Figs. 2, 3): 
Body divided by the equatorial fun into two subequal 
halves, each of which is a low cone, the posterior one truncated. 
Anterior cone formed by six large intermediate plates meeting 
four much smaller unequal end plates in an angle somewhat 
less than one hundred and eighty degrees. Posterior cone of 
five large intermediate and one large end plate, with a narrow 
accessory plate next the longitudinal furrow. Equatorial furrow 
slightly oblique, deep, with toothed edges. Longitudinal fur- 
row broader posteriorly than anteriorly, extending from the edge 
of the posterior end plate to the apex of anterior cone. All 
plates regularly bossed.  Sutural lines raised into high, narrow 
ridges. 
The equatorial flagellum alone is active in ordinary swimming, 
producing a rapid rotary and forward movement. The other, 
which trails behind during such progress, is responsible for the 
spasmodic jerkings occasionally seen: 
The size of the cuirass varies from 25 » in diameter by 29 & 
in length, to 53.4 by 56 p. Cysts average 24 p in diameter. 
They are almost spherical, with granular contents of a brown- 
green color. : Cuirass itself colorless. 
ZOOLOGICAL LABORATORY, UNIVERSITY OF CALIFORNIA, 
September, 1901. 
. 1Since the manuscript was sent to press I have found that Bütschli (Bronn's 
Klassen und deus has noted a similar discrepancy between the original 
description of Gonyaulax and hie on cpeerations, which e eads me to suspect 
er the eres oe Lm ird dace pon 
