248 MEMOIRS OF THE UNIVERSITY OP CALIFORNIA 



The posterior half of the hypocone is a smoothly rounded hemisphere. The sides of the anterior 

 half are subparallel. 



The girdle is premedian in position, its proximal end meeting the sulcus at a distance from 

 the apex of 0.31 and its distal end 0.49 respectively of the total length of the body. Its course 

 around the body is that of a descending left spiral with the distal end displaced posteriorly 

 about three times its own width. The furrow is wide, about 0.08 transdiameter, and is deeply 

 impressed, its sides gradual^ curving outward to meet the surface of the body. The distal end 

 of the furrow is somewhat narrower than the proximal. The sulcus begins near the apex and 

 extends to the antapex in a sliglitly sinuous course. The trough is relatively shallow and fades 

 out near both apices. Posterior to the proximal junction with the girdle the furrow becomes 

 narrow and again below the distal junction it contracts to about half the width anteriorly. 

 Beyond the posterior pore it widens and deepens, but soon fades out without reaching the 

 antapex. The anterior flagellar pore is found at the anterior junction of girdle and sulcus, the 

 posterior pore midway between the distal junction and the antapex. 



The nucleus is an ellipsoidal body, closely filled with fine, moniliform, chromatin strands. 

 These follow its long axis which lies parallel with the major axis of the body. It lies in the left 

 side of the hypocone. quite close to the surface. The major and minor axes of the nucleus are 

 0.58 and 0.41 transdiameters in length respectively. 



A small saeklike pusule opens into each flagellar pore. The cytoplasm is very clear and 

 transparent, its very finely granular structure scarcely evident. Minute green spherul(>s, oil 

 droplets, and a few refractive granules are scattered through it. A single large vacuole, clear 

 grey in color, was found on the right side near the junction of girdle and sulcus. This was 

 slightly irregular in outline and had the appearance of a food body. Another smaller body of 

 the same color was present in the epieone. The cytoplasm is pearl grey in tone. The general 

 color of the organism is given to it by the small, flat, ellipsoidal ehromatophores scattered 

 profusely through the cytoplasm. These are olive ochre in color and are found near the center 

 of the cytoplasm as well as near the periphery. 



DiiviENSioxs. — Length, 53/«; transdiameter, 36m; axes of nucleus, 21m and 15m. 



OccuKRENCE. — A single individual was taken August 6, 1917, with a No. 25 

 net, 4 miles off La Jolla, California, in a haul from 60 meters to the surface in 

 a surface temperature of 21°2 C. 



CoMPAEisoxs. — This is one of the few pelagic species of Guiiuiodinium 

 which shows the presence of distinct ehromatophores. The other pelagic species 

 with chromatojAores found by us include G. cinctum and G. herhaceum. ehro- 

 matophores are a quite common characteristic of the minute forms inhabiting 

 the sand beach, such as G. agile, G. f avion, and most species of Ampluduiium , 

 and are also general among the fresh-water species. It is near G. fascum in 

 proportions, but is more rottmd posteriorly, smaller and more olivaceus. It 

 approaches Gyrodinium ovoideum in form of girdle. 



Gymnodinium rete Schiitt 



Text figure BB, 16 



Gymnodinium rctc Sehiitt (1895), p. 43, pi. 26, fig. 89. 



Description. — Under this name Sehiitt (1895) figures an organism with an elongated, 

 cylindrical body ; girdh' on the left side of the body only, with a groove extending anteriorly 

 from its proximal end : nucleus .spheroidal, filled with chromatin granules ; yellow ochre ehromato- 

 phores ; broad pseudopodium-like fiagellum (?) extending from the girdle at the left latei-al 

 mai'gin of the body. 



