KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 257 



Gymnodinium situla s}). nov. 



Plate 1, figure 12 ; text figure Z, 6 



DiAGXOSis. — This is a medium sized species with i-otund, eiip-shapcd ijody 

 with conif-al epieone ; its length ] .2 transdiameters ; girdle submediau, displaced 

 its own width; snlcus extending from apex to antapex; surface finely striate; 

 colo]', pale dull green yellow. Length, 66/^. Pacific off La Jolla, California, 

 July. August. 



Description. — The body is rotund, .shaped somewhat like a cup with a high conical cover, 

 widest in the girdle region, its leugtli 1.2 transdiameters at the widest part. In cross-section 

 the body is nearly circular with only a slight groove down the midventral sui'faee. The hypocone 

 exceeds the epieone in size, its length being subequal, but its wider transdiameter giving it a 

 greater actual size. Tlie epieone has the shape of a short cone of about 90", with a broad base. 

 The apex is blunt and the sides only slightly convex. It has a length of about 0.45 on the left 

 and 0.50 of the total length on the right side. The hypoeone is cup-shaped with a wide, flaring 

 border at the girdle. The sides taper very slightly towards the posterior end which is broad and 

 rounded, with the central part slightly notched by the distal end of the sulcus. 



The girdle is submediau. Its proximal end joins the sulcus at a distance from the apex of 

 about 0.45 and its distal end 0.50 of the total length of the body. It passes around the body in 

 a nearly transverse direction with a slight deflection posteriorly on the riglit side, which displaces 

 the distal end about one widtli of the girdle. The furrow is wide, about 0.09 transdiameter, and 

 is deeply impressed. The lip on the proximal side is undercut, the distal side of the furrow 

 gradually curving outward to the surface of the body. The borders are irregular in outline, 

 following the .slight undulations of the surface. Tlie sulcus begins at the apex and extends 

 posteriorly to the antapex. It occupies a narrow, deep trougli wliich fades out at the apex. 

 Beyond the posterior flagellar pore it becomes wider and deeper, extending through tlie body 

 to the dorsal surface at the antapex, forming an excavation which deeply notches that part of 

 the body. The borders of the sulcus are smooth in outline. The anterior flagellar pore is found 

 at the proximal junction of the girdle and sulcus, the posterior pore midway between the distal 

 junction and the antapex. 



The nucleus is spheroidal and is found in the right side of the posterior half of the body. 

 Its axis is about 0.3 transdiameter in length. A large sacklike pusule opens into the anterior 

 flagellar pore, a more slender one into the posterior pore. 



The cytoplasm is granular and finely alveolate in structure. This is omitted from the figures 

 for the sake of clearness. A mass of large pink vacuoles occupies the major part of the epieone. 

 A smaller group of pink vacuoles, very much smaller in size, is found near the antapex. Two 

 large, spherical, ochraceous orange-colored bodies or vacuoles and one bluish one were located 

 near the anterior pore. These were presumably food bodies in digestion. Behind these and 

 closely grouped around the anterior pusule and on the right side of the sulcus was a mass of 

 small, highly refractive bodies. These were citron yellow in color, and were evidently of a fatty 

 nature. Nutrition is holozoic. 



The entire surface of the organism is covered with fine, longitudinal, equidistant striae. 

 These were composed of short bhie-green dashes, linearly arranged. The number on the hypocone 

 is about a fourth greater than on the epieone. There are about 30 striae at the girdle on the 

 epieone. The surface of the body is roughened and irregular, presenting a similar outline to 

 that shown in G. pachydermatum. In this form, however, the peripheral, alveolar zone of 

 ectoplasm is not so clearly differentiated as in the other species. The general color of the 

 organism is a pale, dull greenish yellow, shading to chalcedony yellow near the girdle and sulcus, 

 the thickness of the body giving to tlie whole a rich effect. 



