KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 149 



Dimensions. — Length, 17-23/^; transdiameter, 17-21/*; axis of nucleus, 5jt*. 



OccuRREXCE. — Figured by Lemmermaun (1<S96?>) from brackish, stagnant 

 water along the l)ordcrs of the Baltic Sea near Plon, Germany. 



Synonymy. — This form was first described by Lemmermann (1896i) as 

 Proroeoifnoii ovoldcum and the name afterwards (1900) changed to Amphi- 

 diuiion ovoideum. Paulsen uses it as a s}Tionym of Amphidinium opercidatmn 

 Clap, and Lach. In this, however, he is evidently mistaken, as a glance at the 

 two figures (text figs. U, 19, 25) will show. It differs in size and proportions, 

 and particularly in the size and shape of the chromatophores. These Lemmer- 

 mann (1910) found were constant in his cultures and concluded that it formed 

 a valid species. 



Amphidinium pacificum sp. nov. 



Plate 2, figure 13 ; text figure U, 24 



Diagnosis. — A large species with ellipsoidal l)ody, its length 1.75 transdiam- 

 eters, girdle without displacement; sulcus extending from girdle to antapex; 

 pyrite yellow chromatophores. Length, 93/*. Pacific off La Jolla, California, 

 July. 



Description. — The body is ellipsoidal with broad, rounded apices, nearly circular in cross- 

 section, its length 1.75 transdiameters at the widest part. The epicone occupies a relatively 

 small part of the body, its distance from the apex on the dorsal face being only 0.03 of the total 

 length of the body. On the ventral face it extends posteriorly for about 0.49 of the total length 

 of the body, its sides forming an angle of about 60°. Its greatest transdiameter is about 0.14 of 

 the greatest transdiameter of the body. The hypocone is broad, slipper-shaped, widest in the 

 middle and flaring slightly immediately behind the girdle. The antapex is broad and rounded. 



The girdle and sulcus meet at a point distant from the apex 0.49 of the total length of the 

 body. It turns anteriorly at an angle of 30° with the longitudinal plane of the body, for a short 

 distance, beyond which it steepens until near the margin it becomes subparallel with the main axis. 

 On the dorsal face it follows an almost transverse direction across the body, 0.03 of the total 

 length of the hotly from the apex, turning posteriorly on the right ventral face at an angle of 

 about 30° with the main axis and meeting the anterior end of the sulcus without displacement. 

 The furrow is about 0.05 transdiameter in width, and deeply impressed, with smooth, slightly 

 undercut borders. The sulcus extends from the girdle to the antapex as a narrow, somewhat 

 obscure furrow. The anterior flagellar pore is found at the junction of the two ends of the girdle. 



The nucleus is a broadly ellijjsoidal body on the right side of the middle part of the hypocone. 

 Its major and minor axes are about 0.47 and 0.34 transdiameters in length respectively. 



A small sacklike pusule opens into the anterior flagellar pore. The cytoplasm is finely 

 granular and is filled with large alveoli. Near the anterior flagellar pore is a grouji of minute, 

 dark green, refractive granules, mingled with wliicli are a few blue green sj)hernles. In the 

 jjcrijiheral zone are a few ellipsoidal, leaflike chromatophores, pyrite yellow in color. These are 

 most numerous along the lateral margins of the body and near tlu> girdle. 



Dimensions. — Length, 93/*; transdiameter, 53/*; axes of nucleus, 25 and 18/*. 

 (Jcci'RRENCE. — This was taken Jidy 25, 1917, in a surface haul 11 miles off 

 La Jolla, California, in a surface temperature of 21-75 C. 



