KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 373 



The hypocone on its left side has a length of 1.85 and on its right of 0.45 transdiameters. It is 

 thus a trifle smaller than the epicone. 



The girdle is a descending left spiral of 1.5 turns, displaced about 0.6 of the total length of 

 the body. It turns posteriorly at an angle of about 45° with the transverse plane, but the angle 

 gradually becomes less, the latter part of its course having a slope of 30°. The furrow has a 

 width of about 0.06 transdiameter and is deeply impressed with its trough undercutting the 

 anterior border. The anterior end of the sulcus forms an apical loop which passes around the 

 short anterior process at the apex terminating on the right side. It passes posteriorly as a very 

 slender, faintl.v develoi)ed furrow, until it reaches the proximal end of the girdle, where it 

 suddenly expands and for the rest of its course has a width somewhat more than half the width 

 of the girdle, with a deeply impressed furrow, fading out before reaching the antapex. The inter- 

 cingular portion makes a turn of 0.5 transdiameter. The complete torsion is difficult to estimate, 

 as the anterior loop reverses its usual direction and passes from right to left around the apical 

 process, turning again to the left in the usual direction near the anterior pore region. The 

 posterior portion also swings to the right beyond the ])osterior pore. The anterior and posterior 

 flagellar pores are located at the anterior and i)roximal junctions of the girdle and sulcus 

 respectively. 



The nucleus is a spheroidal body lying near tlie center, slightly posterior to the midplane. 

 It is differentiated into two zones, an outer, clear, hyaline perinuclear zone and an inner region 

 filled with coarse moniliform chromatin strands. The outer zone is narrow, about 0.07 of the 

 total transdiameter of tlie nucleus in width, and is composed of alveoli surrounded by a double- 

 contoured membrane. The axis of the nucleus is about 0.5 transdiameter of the body in length. 



The cytoplasm is clear and transparent and pale greenish yellow in color. A number of 

 food vacuoles were present, one of irregular shape and of a pale lu'own color near the posterior 

 pore close beside the nucleus, and several spherules of varying sizes, bluish or pink in color, 

 scattered througli the anterocentral part of the body. Nutrition, as in most if not all of the 

 species of CocModinium, is holozoic. In the posterior region were two long, slender, })lue-green 

 rhabdosomes, about 0.8 transdiameter in length, lying in the plane of the surface with tlieir ends 

 at the antapex. 



The surface is finely striate with equidistant, blue-green, broken lines, about 45 on tlie 

 ventral face of the epicone at the girdle. These are about four times as numerous on the epicone 

 as on the hypocone. Irregular splashes of seai'let jiigment are scattered through the peripheral 

 layer in close relation to the striae, but not confined to single lines as in Gyrodinium coralli num 

 (pi. 10, fig. 117). These are confined almost exclusively to the epicone in the individual figured. 



Dimensions. — Length, 175-205/*; tran.sdiameter, 85/*; axis of nucleus, 45/*. 



OccuERENCE. — Taken on July 9, 1907, in a haul made with a No. 12 net 

 from 120 meters to the surface, 2.5 miles off La Jolla, California, in a surface 

 temperature of about 20° C. 



Comparisons.— In its red i)igment and t,vpe of nuclear structure this species 

 resembles Gyrodinium corallinum (pi. 10, fig. 117), G. virgntum (pi. 10, fig. 

 112), and Gijninodiinum ruhnrm (pi. 8, fig. 86). "With Cochlodinium MniU(/i(- 

 latmn (fig. (JG, 8) it is the largest s]iecies in this genus and next to the largest 

 thus far described in the G^aimodinioidae, Gij»inodinium cucumis (fig. Y, 16), 

 210/* in length, alone exceeding it. 



It forms the type of a large grouj) of species of the subgenus Cochlodinium 

 characterized by a torsion of the liody represented by 1.5 turns of tlie girdle. 

 This amount of torsion |>hiccs the group near the genus G/jrodinium, and in 

 the case of Cochlodiniuni niiiKituin this relationship is still further strength- 

 ened by the striate surface, characteristic of many species of Gyrodinium. 



