KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 339 



color and in its surface markings, the latter being entirely absent in G. flavidtim. 

 There is a difference between the two in their apices, which are nmch more 

 developed in G. flavidum than in G. tnincus. 



Gyrodinium virgatum sp. nov. 



Plate 10, figure 112 ; text figure DD, 21 



Diagnosis. — This is a stout medium sized species with subrhomboidal liody, 

 its length 1.45 transdiameters ; girdle a descending left spiral, displaced 0.73 

 transdiameter ; sulcus extending from apex to antapex ; surface coarsely striate ; 

 color, greenish yellow with coral-red pigment. Leng-th, 93^. Pacific off La 

 Jolla, California, August. 



Description. — The body is asymmetrical, subrhomboidal in shape, tapering conical anteriorly, 

 its length 1.45 transdiameters at the widest part, which is at the girdle. In cross-section the 

 body is nearly circular. The epicone and hypoeone are subequal in size. In the individual 

 figured the posterior end was truncate and drawn out to tlie left, as though having recently 

 discharged a food body. A second individual showed the posterior end having a shape somewhat 

 similar to the anterior end. The epicone is broadly conical, subtending an angle of about 80° 

 with the right side almost twice the length of the left, and the apex narrowly rounded. The 

 length of the epicone on the left of the sulcus is 0.21 and on the right is 0.72 of the total length 

 of the body. The hypoeone is distorted in the individual figured in that the antapex is drawn 

 out on the left side to a broadly truncate form. A second individual in the same material 

 showed the hypoeone slightly rounder than the epicone with a broadly rounded antapex. Both 

 epicone and hypoeone form wide, flaring shelves at the girdle region. 



The proximal and distal ends of the girdle join the sulcus at about 0.21 and 0.72 respectively 

 of the total length of the body from the apex. The girdle sweeps around the body in a descending 

 left spiral course which is displaced at the right side posteriorly 0.71 transdiameter. The fuiTOW 

 has a width of about 0.05 transdiameter, and is deeply impressed with broad, flaring borders 

 raised above the surface of the body. The anterior flagellar pore is located at the jiroximal 

 junction of the girdle and sulcus and the posterior pore slightly below the distal junction. 



The sulcus is a wide, deep trough which extends from tlie apex to the antapex in an almost 

 straight line. It varies slightly in width throughout, narrow anteriorly and wider posteriorly, 

 with smooth rounded borders. 



The nucleus is large, kidney-shaped and is located slightly below the equatorial plane. It is 

 differentiated into two parts, an outer alveolar layer and an inner region filled with large 

 chromatin granules without linear arrangement. The outer layer is about 0.1 of the minor axis 

 of the nucleus in thickness and is compo.sed of ellipsoidal, pink vacuoles arranged with their 

 long axis perpendicular to the surface of the nucleus. The nuijor and minor axes of the nucleus 

 are 0.6 and 0.3 transdiameter in length respectively. 



A large, sacklike pusule opens into the anterior flagellar pore. The cytoplasm is very finely 

 granular, clear and transparent. A large pink vacuole in the antapieal region and numerous 

 dark refractive bodies were present, the products, probably, of holozoic nutrition. The general 

 color of the cytoplasm is greenish yellow. The surface is striate with rather widely separated, 

 equidistant, blue-green striae. These are more numerous on the hypoeone, the epicone containing 

 approximately one-half the number on the hypoeone. The striae on the epicone are beset with 

 masses of eoral-red pigment and number 15 across the ventral face. The pigment may take the 

 form of beads or long masses following the line of striae, or of irregular splashes. Several large 

 rounded masses of coral red were located near the apex. A few granules of coral red were 

 found on the hypoeone. 



