338 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Gyrodinium truncus sp. nov. 



Plate 3, figure 28 ; text figure DD, 4 



Diagnosis. — A large species with body rotitnd, suliellipsoidal, its length 1.48 

 trausdiameters ; girdle a descending left sjDiral, disjjlaced 0.64 transdiameters ; 

 sulcus extending from apex to antaj^ex ; surface coarsely striate ; color, greenish 

 yellow. Length, SSy-. Pacific off La Jolla, California, August. 



Description. — The body is large, of robust habit, and asjinnietrical outline, its length 1.48 

 transdiameters at the widest part, ■vrhieh is below the girdle. The posterior end is pointed and 

 the anterior end is as^^nmetrical and almost truncate in outline with the girdle region on the 

 left side forming a high shoulder. A cross-section of the body is nearly circular. The hypocone 

 greatly exceeds the epicoue in size, its length being greater by 0.39 of its own length. The epicone 

 is somewhat excentric, the left side being raised, forming an angle of 60° with the longitudinal 

 axis of the body and terminating in a high, shoulder-like ridge about 0.09 of the length of the 

 body below the apex. The epicone lengthens until it reaches 0..54 of the total length of the body 

 on the right side of the sulcus. The apex is broad and truncate in outline. The hypocone is 

 very broad with rounded sides which contract abruptly to a point at the antapex. which is 

 notched on the left side by the distal end of the sulcus. 



The girdle is a descending left spiral, which meets the sulcus proximally about 0.09 of the 

 total length of the body below the apex. Its distal junction with the sulcus occurs at 0.54 of 

 the total length of the body below the apex, giving it a displacement of 0.64 transdiameters. 

 It lies in a wide, deep depression, its width about 0.05 transdiameter, with smoothly rounded, 

 overhanging borders, both of which are undercut by the furrow. The anterior flagellar poi'e 

 is located at the anterior junction of the girdle and sulcus and the posterior poi-e far po.sterior, 

 less than 0.2 transdiameter from the antapex. The transverse flagellum was short, traversing 

 but a short proximal section of the girdle. 



The sulcus extends from the apex to the antapex. Below the anterior flagellar pore it lies 

 in a shallow trough with overhanging sides, the borders of which are unevenly serrate, the right 

 border extending bej'ond the left in a flap which obscures the furrow. 



The nucleus is large, ellipsoidal and situated slightly below the central portion of the body, 

 with its long axis oblique to that of the body. Large, moniliform chromatin tlireads follow its 

 major axis. Its major and minor axes are 0.71 and 0.5 transdiameters in length respectively. 



A small sacklike pusule opens into each flagellar pore. The cytoplasm is very finely granular, 

 and contains food bodies and other e\-idences of holozoic nutrition. In the individual figured 

 two large, irregidar-shaped, yellowish green and greyish green food bodies were found close 

 beside the nucleus. In the epicone were three groups of dark, refractive oil globules. Smaller 

 blue-green oil droplets were scattered through the anterior half of the body. The general color 

 of the protoplasm is yellowish green in the anterior portion of the body shading to a yellow 

 ochre and old gold in the antapical region. The surface of the body is striate with blue green, 

 equidistant lines extending from the girdle to the apices, 15 in number across the ventral face 

 of the epicone. These are about l/x apart on the epicone and 4/j. on the hypocone side of the 

 girdle. 



Dimensions. — Length, 83," ; transdiameter, 55/^ ; axes of nucleus, 42m and 27/'. 



OccuREExCE. — A single individual was taken Augxist IT, 1917, with a No. 25 

 silk net. 0.75 mile off La Jolla, California, in a haul from SO meters to the 

 stirface and in a surface temperature of 21-9 C. 



Comparisons. — In the unusual as^mimetry of the body this form closely 

 resembles G. flavidum sp. nov. (fig. CC, 20), differing from it, however, both in 



