KOPOID AND SWEZY: UNARMORED DINOFLAGELLATA 189 



greatly in width, being usually wide at the girdle and at the posterior end of its course which is 

 near the antapex. The anterior flagellar pore opens at the junction of the proximal end of the 

 girdle and tlie sulcus and the posterior pore at their distal junction. 



The nucleus is a large, ellipsoidal body located anterior to the equatorial plane. It is filled 

 with fine, moniliform chromatin strands and shows a distinct double-contoured mcmbi-anc sur- 

 rounding it. Its major and minor axes are 0.46 and 0.52 transdiameter respectively. The 

 cytoplasm is coarsely granular and was quite free from food bodies and vacuoles in the specimens 

 examined. The surface is striate with longitudinal, equidistant blue-green striae composed of 

 linear series of short broken lines. These are about tlie same number on both epicone and 

 hypocone, approximately 16 across the ventral face. The color of the organism is a clear 

 strontium yellow, diffused through the cytoplasm. It is probably holozoic in its nutrition. 



Dimensions. — Length, 83;^; transdiaiiicter, 45/*; dorso ventral diameter, 39/1 ; 

 major and minor axes of nucleus, 13/* and 11/* respectively. 



Occurrence. — This was first observed July 11, 1906, in a haul with a No. 20 

 net, 2 miles oi¥ La Jolla, California, from 155 meters to the- surface and in a 

 surface temperature of 20?9 C. It was found July 9, 1917, in a haul with a 

 No. 25 net, 4 miles offshore, from 80 meters to the surface and in a surface 

 temperature of 19?8 C. 



Comparisons. — This species bears a strong resemblance to Gymnodinium 

 helveticum Penard. Penard's (1891) species, however, is a fresh- water form 

 from Lake Geneva, Switzerland. Our species is probably the marine repre- 

 sentative of the same group. Its size and proportions differ somewhat from 

 those of G. hcJvcticuni and it has a greater displacement of the girdle. It be- 

 longs to the subgenus Lineadinium , but, aside from G. helveticum, there are no 

 other species closely resembling it. 



Gymnodinium bicaudatum Pa^illard 



Text figure BB, 9 



Gymnodinium bicaudatum Pavillard (1905), p. 47, pi. 3, fig. 5. 



This organism was described by Pavillard (1905) from the Gulf of Lyons 

 and seems to have suggestions in its s^anmetry of the characteristics of the 

 thecate genus llcterodiuinm Kofoid. The data given are not sufficient to place 

 it in Gymnodhnu)}!, or to define its specific characters. The two posterior 

 projections are quite unlike anything in the unarmored dinoflagellates. It may 

 "be a thecate form recently escaped by exuviation of the skeleton and therefore 

 temporarily non-thecate. The possil)ility of approaching division or of an 

 antapical vent following ejection of food l)alls in an unarmored species is not 

 precluded as an exi^lanation of the bifurcated postmargin. 



