CHAPTER XII 



GYMNODINIID AE : GYMXODIXIOI (continued), G. HAMULUS TO 



G. ZACHARIASI 



Gymnodinium hamulus sp. boy. 



Plate 9, figure 97 : text figure Y, 5 



DiAGXosis. — A minute species with discoidal dorsoTentrallr compressed 

 body, its length and transdiameter suhequal; girdle snbmedian. without dis- 

 ]3lacement: sulcus extending from girdle to antapex; surface striate; color 

 green. Length, 16.5m. Sand beach at La Jolla, California, July. 



Descriptiox. — The body is discoidal, rotund in ventral view and dorsoventrally flattened, 

 its dorsoventral diameter 0.61 of its transdiameter and its length and transdiameter subequal. 

 In lateral view the dorsal surface is more convex than the ventral. The epicone and the hypocone 

 are subequal. The epicone is semicircular in shape in ventral view with the short pointed apex 

 sharply deflected to the left and dorsad. Its greatest length is 0.5 of the total length of the 

 body. The hypocone is slightly broader than the epicone, with rounded sides and antapex 

 broadly notched by the distal end of the sulcus. In lateral view the ventral side shows a slight 

 sigmoid curve in its surfar-e with the dorsal side convex. 



The girdle is submediau in position, its greatest distance from the apex being 0.5 of the total 

 length of the body. It forms a complete circle around the body with a slight deflection poster- 

 iorly on the ventral face at its junction with the sulcus. The furrow is wide, about 0.11 trans- 

 diameters, and rather deeply impressed with smooth borders. The sulcus is wider than the 

 girdle, expanding to nearly twice its width anteriorlj^ at the junction with the girdle and slightly 

 more posteriorly, where the borders are widely deflected and extend around to the dorsal surface, 

 forming a deep sulcal notch at the antapex. The anterior flagellar pore is found at the union 

 of the two ends of the girdle, the posterior pore about one width of the girdle posteriorly. 



The nucleus is spherical and is located slightly posterior to the central part of the body. 

 Its axis is about 0.27 transdiameter in length. 



The cytoplasm is clear and contains numerous blue-green spherules. The siirface is striate 

 with blue-green striae, which are equidistant and parallel throughout their length, and about 

 twenty in number across the ventral face and equal in number on epicone and hypocone. The 

 general color of the organism is blue green. In many individuals a small red-brown mass, 

 probably a food body, is found in the epicone. 



Dimensions. — Length, IG.'j/x; transdiameter, 16^; dorsoventral diameter, 

 about If ; axis of nucleus, 5/^. 



OccuEREXCE. — This species was found very abundantly in the beach sands 

 at lia Jolla, California, in July, 1914. On August 13 and 15, 1917, several 

 individuals were observed in the hauls made 0.75 mile offshore from 83 meters 

 and 70 meters to the surface respectively. 



CoMPAEisoxs. — This is one of the smallest of the G}innodiniidae, a single 

 species, the fresh-water G. varians, 11/' in length, being smaller. It is typically 

 a sand-beach form, and shows, in the dorsoventral compression of the body, a 



[218] 



