KOPOID AND SWEZY: UNARMORED DINOFLAGELLATA 317 



figured was taken August 18, 4 miles offshore, from 80 meters to the surface 

 and in a surface temperature of 20-2 C. 



AcTiTiTiES. — Tliese are active little forms in constant motion until slowed 

 down by the adverse conditions found under the ndcroscope. They move about 

 in a loose spiral with a slow, clockwdse rotation, varied with short periods of 

 ra])id whirling with the dorsal side uppermost. 



CoMrAiiisoxs. — This is one of the few species below Pouchctia which 

 possess pigment capal)le of active movement, and is probably near the line of 

 evolution of that genus. The other members of Gyrodinmm. w^hich are aligned 

 with it in this respect are G. ocliraccum, G. coraUinum, and G. virgatum. In 

 its girdle arrangement this species shows a close relationship with G. fissiim 

 (fig\ DD, 8), G. corallimim (fig. DD, 12), and G. pingue (fig. DD, 15). The 

 surface striae are also like those of G. contllinum and G. fissum. 



Gyrodinium melo sp. nov. 



Plate 5, figure 50 ; text figure CC, 9 



Dtaoxosis. — A medium sized species with rotund ovoidal body, its length 

 1.42 transdiameters ; girdle a descending left sjjiral, displaced 0.53 transdiam- 

 eter : sulcus extending from apex to antapex ; color, grey with green chromato- 

 phores. Length, GGm-. Pacific off La Jolla, California, July. 



Description. — Tlie body is rotund ovoidal, rounded posteriorly, tapering slightly anteriorly, 

 its length 1.42 transdiameter at its widest part, which is equatorial in location. In cross-section 

 the body is circular in outline. The hypocone exceeds the epicone in size, having a slightly 

 greater length and a continuously greater transdiameter. The epicene has rounded sides and a 

 short bluntly acuminate apex. It has a length on the left and right sides of 0.19 and 0.53 

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

 symmetrically rounded antapex. 



The girdle is a descending left spiral with a displacement of 0.53 transdiameter and an 

 overhang of about 0.25 transdiameter. Its proximal end joins the sulcus at a distance from the 

 the apex of 0.19 of the total length of the body. For the first 0.5 transdiameter of its course its 

 direction is transverse l)eyond which it turns posteriorly on the dorsal face at an angle of about 

 55°, joining the sulcus distally about 0.53 of the total length of the body from the apex. The 

 furi'ow has a width of about 0.06 transdiameter and is deeply impressed with smooth borders. 

 The sulcus invades the epicone nearly to the apex and extends posteriorly to within a shoi't 

 distance of the antapex in a sigmoid line. It is rather shallow and fades out near the apices. 

 The anterior flagellar pore opens at the proximal junetion of the girdle and sulcus, the posterior 

 pore about two widths of the girdle tielow the distal junction. 



The nucleus is a large spheroidal body filled with coarse, monilifonu cliromatin strands. It 

 is located dorsad to the intercingular area. Its axis is about 0.34 tran.sdiameter in lengtli. 



The cytoplasm is coarsely granular and contains food masses, vacuoles, and a few minute, 

 refractive granules. In the posterior ])art of the individual figui-ed is a large, orange-rufous 

 body, with a smaller body, brighter red in color, lying near it. In the anterior part of the body 

 are three large vacuoles, one filled with a blue fluid, the otliers with a grey fluid. Tlu; general 

 color of the cytoplasm is grey with darker tones in the jieriplieral zone. This zone also contains 

 the irregular, leaflike, apple-green chromatophores. Nutrition is possibly both holophytic and 

 holozoie, as the |)resence of both chromatoiihores and foo<l liodies in tlie cytoplasm may indicate. 



