KOPOID AND SWEZY: UNARMORED DINOFLAGELLATA 327 



species from all others in the genus. The nearest approach to it is found in 

 G. lachrjjma (Meunier), a nuieh more attenuate and slender species, whose 

 surface structure is unknown. 



Gyrodinium pingue (S(;hiitt) 



Plate 4, figure 38; text figure DD, 15 



Gymnodinium spiralc var. pivgiiis Schiitt (1895), pi. 21, fig. 65. 

 Spirodinium spindr var. pinc/uc, Lemmermann (1899), p. 359. 



Diagnosis. — A small species with elongated ovoidal l^ody, its length 1.88 

 transdiameter ; girdle a descending left spiral, displaced 0.74 transdiameter ; 

 sulcus extending from near apex to antapex ; surface finely striate ; color, pale 

 lumiere green. Length, 51/^ Pacific off La Jolla, California, July; Atlantic 

 or Bay of Naples. 



Description. — The body is ovoidal, circular in cross-section, broadly rounded posteriorly, 

 narrowly so anteriorly, its length 1.88 transdiameters at the widest part in the upper hypocone. 

 The hypocone exceeds the epicone in size, having a continuously broader transdiameter, though 

 the lengths are approximately the same. The epicone is convex conical, forming an angle of 

 about 70°, with a blunt apex. It has a length on the left and right sides of 0.25 and 0.66 

 respectively of the total length of the body. The hypocone is elongate hemispherical posteriorly 

 with a broad antapex. It has a length on the left and right sides of 0.68 and 0.27 of the total 

 length of the body. 



The girdle is a descending left spiral with its proximal and distal ends joining the sulcus at 

 a distance from the apex of 0.25 and 0.66 respectively of the total length of the body. In the 

 first 0.5 transdiameter of its course its direction is slightly deflected anteriorly, turning poster- 

 iorly on the dorsal surface and continuing on the ventral surface in a steep spiral with its distal 

 end displaced 0.74 transdiameter. The furrow has a widtli of about 0.09 transdiameter, and is 

 deeply impressed with smoothly rounded borders. Tlie sulcus extends from or near the apex 

 posteriorly to the antapex in a slightly sinuous line. Its wi<ltli is about half that of the girdle 

 and is rather shallow, fading out near the antapex. 



The nucleus is spherical in shape and is located at or near the center of the body. It is filled 

 with fine moniliform chromatin strands. Its axis is about 0.4 transdiameter in length. 



A large, saeklike pusule opens into the posterior flagellar pore, and is sometimes present at 

 both pores. The cytoplasm is usually dense and alveolar in structure, often containing many 

 inclusions, such as greenish refractive spherules, blue-green oil droplets and larger food masses 

 indicative of holozoic nutrition. A peripheral zone of short, l)lne-greeii rodlets is often present. 

 The color of the cytoplasm is pale lumiere green difl'usiHl tlirougliout. The surface is finely 

 striate, the striae varying somewhat in different individuals. In most of the specimens examined 

 these consist of blue-green, equidistant lines. In otlier forms the lines may be broken by minute 

 blue-green granules strung along tlieir length like beads on a tliread or giving the appearance of 

 a dot and dash (pi. 4, fig. 38). 



Dimensions. — Length, 45-51/^; transdiameter, 30-27/*; axis of nucleus, 11^. 



OccuEEENCE. — This was first recorded for this region July 13, 1906, in a 

 surface haitl taken with a No. 20 net near La Jolla, California. On July 10, 

 1906, it was again found in a surface haul. It was frequently seen during July 

 and August, 1917, l)()th in the surface haids made at the end of the pier at the 



