KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 239 



The nucleus is a relatively large, ellipsoidal body filled with coarse, moniliform chromatin 

 strands. It is located on the left side of the anterior part of the body. Its major and minor 

 axes are 0.53 and 0.42 transdiameters respectively. 



No pusules were observed. The cytoplasm is finely granular and usually contains one or 

 more large food bodies. The one figured contained a single large, reddish brown mass, nearly 

 filling the entire body. Other individuals showed one to several food bodies yellow ochre in 

 color. Nutrition is holozoie. The color of the cytoplasm is pearl grey. It is made conspicuous 

 under the microscope by the presence of the brightly colored food bodies. 



Dimensions. — Lengtli, 28/^ ; transdiameter, 28/^ ; axes of nucleus, 15/^ and 12^^. 



Occurrence. — This was observed July 9, 1914, in a surface haul taken near 

 the shore at La Jolla, California. In July and August, 1917, it was frequently 

 met with in most of the hauls made. The one figured was taken July 21, with 

 a No. 25 net in a surface haul at the end of the pier. 



Comparisons. — The group of minute species represented by G. ovulum, G. 

 minor, G. vorticella, G. mariniim, and a few fresh-water forms must be regarded, 

 only tentatively as good species. The similarity of these forms to the small 

 Gymnodinium found in cysts, evidently the products of multiple fission, leads 

 one to suspect that we may be dealing here with a stage in the life history and 

 not with distinct species. The great difficulty in following the development of 

 these extremely delicate organisms leaves this an open question at the present 

 time. For the sake of convenience, therefore, they are held as valid species 

 until their development has been followed out more fully. Among marine 

 species G. ovulum is nearest G. minor Lelwur (fig. X, 12) and G. favum. sp. nov. 

 (fig. X, 7), but is more nearly spherical than either and lacks the chromato- 

 phores of the latter. The distension of the l)ody by the food balls is possibly a 

 factor in its spheroidal contour. 



Gymnodinium pachydermatum sp. nov. 



Plate 3, figure 32 ; text figure AA, 5 



Diagnosis. — This is a large species of robust habit, body broadly ellipsoidal, 

 its length 1.53 transdiameters; epicone hemispherical; girdle submedian; dis- 

 placed twice its own width ; sulcus invading the epicone, extending to the anta- 

 pex: differentiated ectoplasm; color orange green. Length, 160^. Pacific off 

 La Jolla, California, June, July. 



Description. — The body is of robust habit, broadly clliiisoidal with broad apices, nearly 

 circular in cross-section, with protuberant girdle, its length l.r)3 transdiameters at the widest 

 l)art. The epicone and hypoeone are subequal in length, but tlie transdiameter of tlie distal 

 part of the epicone is slightly greater than tlic greatest transdiameter of the hypoeone. The 

 epicone is broadly dome-shaped, hemispherical anteriorly and flaring slightly at the girdle. The 

 apex is broad and symmetrically rounded. The epicone has a lengtli on the left and right sides 

 of 0.4 and 0.53 respectively of the total length of the body. The hypoeone is somewhat narrower 

 than the epicone with sides subparallel anteriorly ami rounded posteriorly with the antapex 

 deeply notched by the distal end of the sulcus. 



