260 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



pointed apex. It has a length of 0.5 of the total length of the body. The hypoeone is sub- 

 hemispherical iu shape, broadly notched at the antapex by the distal end of the sulcus. The 

 left side is slightly sigmoid in outline, the riglit side nearly sti'aight. The posterior end is 

 bilobed in ventral view with two short, broadly rounded lobes. 



The girdle is subraedian and forms a complete circle around the body. Its distance from the 

 apex is about 0..5 of the total length of the body. The furrow is wide, about 0.08 transdiameter 

 and rather shallow, with smoothly rounded borders. The sulcus begins at the apex and extends 

 posteriorly in a slightly sinuous line to the antapex. The furrow is narrow and lies in the 

 middle of a wide trough which indents the ventral svirface of tlie body. Posterior to the posterior 

 pore it becomes wide and deep, reaching through the body to the dorsal surface, and forming a 

 deep excavation at the antapex. The anterior flagellar pore is found at the proximal junction 

 of the girdle and sulcus, the posterior pore midway between the girdle and antapex. 



The nucleus is a spheroidal body found on the left side of the epieone. It is tilled with 

 moniliform chromatin granules. Its axis is about 0.33 transdiameter in length. 



A large club-shaped pusule opens into each flagellar pore. The cytoplasm is very finely 

 granular, clear and transparent. A single large, green yellow food mass was present near the 

 nucleus. This was enclosed in a much larger food vacuole. The color of the organism is a dull 

 rose red ditfused throughout the cytoplasm. Near the apices particles of the coloring pigment 

 were condensed into small globules of bright rose red color. These were slightly more numerous 

 at tlie antapex than at the apex. On the surface of the hypoeone are a number of ridges begin- 

 ning below the girdle and extending posteriorly to near the antapex. These were four in 

 number on the ventral face and six on the dorsal. They are yellow in color, narrow and raised 

 slightly above the surface. None could be detected on the epieone. No other surface markings 

 were present. 



Dimensions. — Length, 63/^ ; transdiameter, 60^^ ; axis of nucleus, 20^1. 



Occurrence. — A single indi'vidual was taken August 6, 1917, with a Xo. 25 

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

 and in a surface temperature of 21? 9 C. 



CoMPAEisoNS. — This species and G. co)itracti()H and G. rKhricauda have 

 several features in common. The girdle forms a complete circle around the 

 body and the general color is the same. Ridges are present on the epieone in 

 G. contractum and are entirely absent in G. ruhricaudn. The enclosure of food 

 bodies in a conspicuous vacuole is common to both G. sulcatum and G. con- 

 tractum. The girdle is submedian in the three species. The possibility that 

 these three are varieties of one species cannot be overlooked. However, many 

 specimens of G. contractum and G. ruhricauda were observed and these showed 

 no intergradations of form. The solitary individual of G. sulcatum makes that 

 species a more doubtful one. 



Gymnodinium tenuissimum Lautcrborn 



Text figure AA, 7 



Gymnodinium tenuissimum Lauterborn (1894), pp. 391, 396; (1898), p. 388, pi. 18, fig. 



26; (1910a), p. 464; (1910&), p. 499; (1913), p. 906. 

 G. tenuismmum, Lemmermann (1900), p. 116; (1902), p. 260; (1910), pp. 565, 618, 621, 



fig. 21. 

 G. tenuissimum, Zschokke (1900), p. 43. 

 G. tenuissimum, Lang (1901), p. 25, fig. 41. 

 G. tenuissimum, Schilling (1913), p. 18, fig. 17. 



