KOFOID AND SWEZY: UNAKMORED DINOFLAGELLATA 253 



the color sliades from dalilia purple in G. postmaculatum, to coral red in G. 

 coraUlnum. In PoucJictia the color in this i>-roup varies from amaranth purple 

 in P. purpurescens to dahlia purple in P. pit rpii rata and spinel red in P. voracis. 

 Gymnodinium ri(bricanda helongs in the subgenus Gymnodinium, as do most 

 of the species Avith colored pigment in the genus. It belongs to the group, in 

 the subgenus GijiHuodiniion, which includes G. sulcatum, and G. contractum, 

 in which the differences are mainly in proportions, distrilnition of the color, 

 and the extent of the sulcus. The sulcus extends from apex to antapex in G. 

 sulcatum and G. ruhrum (figs. X, 1 ; Y, 4), but is confined to the hypocone in G. 

 contractum (fig. X, 2). In addition to these peculiarities the surface of G. 

 ruhricauda is entirely devoid of striae, while feeble markings occur on the 

 In^jocone of G. sulcatum and on the epicone of G. contractum. In view of the 

 number of individuals conforming to these differences, seen in the case of G. 

 sulcatum and G. ruhricauda, we conclude that they are not phases of one and 

 the same species. 



Gymnodinium rubrum sp. nov. 



Plate S, figure 86 ; text figures A, Y, 4 



Diagnosis. — This is a large species with ovoidal body, its length 1.81 trans- 

 diameters; girdle su])niedian, descending left spiral, displaced 0.37 transdiam- 

 eter : sulcus extending from apex to antapex in a sinuous course ; surface striate ; 

 color pale glaucous green and rose red ; remarkably labile in form. Length, 145/*. 

 Pacific off La Jolla, California. July, August. 



Description. — The body is quite labile and variable in shape, normally ovoidal, circular in 

 cross-section, widest anteriorly, with broad, rounded apices, its length 1.81 transdiameters at 

 the widest part. Individuals showing great metabolic changes and distortions are frequently 

 met with (fig. A). These variations include rounded-up forms and larger ones with deepl.v lobed 

 apical or antapical ends. The epicone and hypocone are subequal in length, but the usually 

 greater transdiameter of the epicone increases its relative size slightly. The epicone is rounded 

 to conical in shape with broad apex. It has a length on the left and right sides of 0.4 and 0.59 

 respectively of the total length of the body. The hypocone is more asymmetrical than the 

 epicone with greater irregularity in its outline. The antapex is broad and rounded and more 

 or less deeply notched by the distal end of the sulcus. 



The girdle is submedian in position, its proximal end joining the sulcus at a distance from 

 the apex of 0.4 and its distal end at 0.59 of the total length of the body. It follows a descending 

 left spiral course around the body with a posterior displacement of its distal end of 0.37 trans- 

 diameter and with an overhang of about 0.01 transdiameter. The furrow is wide, about 0.06 

 transdiameter, and deeply impressed, its overhanging borders raised considerably above the 

 surrounding surface of the body. 



The sulcus usually begins at or near the apex and extends posteriorly to the antapex. It 

 follows a slightly sinuous course on the epicone and is deflected sinistrally at an angle of about 

 20^ below the anterior junction with the girdle. After passing the distal junction it again 

 assumes a nearly longitudinal direction and continues thus to the antapex. Throughout its 

 course it occupies a deep trough which widens to twice its anterior transdiameter beyond the 



