KOFOID AND SWEZY: UNARMOKED DINOFLAGELLATA 139 



ventrally, witli the left side longer and sliglitly less convex than the right. The antapex is exca- 

 vated ventrally by the sulcal notch, broad and rounded on the dorsal side, the right and left 

 borders of the sulcus extending posteriorly in slender, toothlike points. 



The girdle is somewhat asymmetrical in position, located about 0.1 of the total length of the 

 body below the apex on the dorsal side, with the distance less on the left and slightly greater on 

 the right sides. Ventrad, both ends turn posteriorly and meet at a point distant from the apex 

 about 0.3 of the total length of the body. The furrow is wide, about 0.09 transdiameter, and 

 deeply impressed, with overhanging borders. The sulcus extends from the girdle to the antapex 

 in a slightly sinuous line which flares widely in the distal half of its course, at the same time 

 expanding dorsad, deeply excavating the ventral part of the body. The anterior flagellar pore 

 opens at the junction of the girdle and sulcus, the posterior pore slightly posterior to the mid- 

 point between girdle and antapex. 



The nucleus is an ellipsoidal body found on the left side of the sulcus below the girdle. Its 

 major and minor axes are about 0.46 and 0.25 transdiameters in length, respectively. A large 

 sacklike pusule opens into each flagellar pore. These are connected below their openings by a 

 slender canal. The cytoplasm is clear and colorless. In the peripheral layer are numerous, 

 disklike chromatophores of a dull, blue green color and many minute, dark, highly refractive 

 granules. No striae or other surface markings could be detected. 



Dimensions. — Length, 40/*; transdiameter, 32/*; axes of nucleus, 15 and 8/*. 



OccuREENCE. — Tliis species was found in the beach sand at La Jolla, 

 California, in August, 1917. 



Comparisons. — This species has much in conmion with ^1. truncatum (fig. 

 TJ, 3). The size and shape of the epicone and the lack of surface striae serve, 

 however, to set it ajoart from that species. 



Amphidinium discoidalis Diesing 



Text figure U, 23 



Amphidinium opcrculafum Claparede and Laehmann (1858-61), p. 411, pi. 20, fig. 12 only. 

 A. operculatum> var. discmdalis Diesing (1866), p. 98 (384). 



Diagnosis. — A small sijccies with broadly ovoidal Ijody, its length, 1.13 trans- 

 diameters ; girdle anterior ; sulcus ( ?) ; colorless. Length, 47/*. North Sea on 

 the coast of Norway. 



Description. — The body is broadly ovoidal, widest posteriori}-, its length 1.13 transdiameters 

 at the widest part. The epicone is minute, with a length of about 0.05 of the total length of tlie 

 body. The apex is broad and truncate. The hypocone is very broad posteriorly, narrowing 

 anteriorly, with broad, rounded antapex. A dorsal view only of this form is given by Claparede 

 and Laehmann (1858-61 ), hence the structure of the ventral surface is unknown. The girdle is 

 far anterior and passes transversely across the dorsal side of the body. Its distance from the 

 apex is about 0.05 of the total length of the body. The cell contents as figured by Claparede and 

 Laehmann consist of a few spherules and rod-shaped bodies, probably oil drops and food masses. 



Dimensions. — Length, 47/*; transdiameter, 41/*. 



OcOTTRRENCE. — Figurcd by Claparede and Laehmann (1858-61) from the 

 North Sea on the coast of Norway. 



