KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 309 



uppermost with no rotation on the axis of tlie body. Occasionally there was a 

 spasmodic rotation of the body in an anticlockwise spiral, rarely in the reverse 

 direction, on its main axis. Not infrequently the organism would rise from 

 the substrate and turn a somersault backward from the previous direction of 

 progress and then resume the spiral gyrations. 



Syxoxymy. — In Miss Lebour's figures she gives as surface striae what seems 

 to correspond to the long, slender rodlets in our form. In her figure, 13&, these 

 pass throixgh the girdle, a condition never foimd in surface striae which termi- 

 nate at or near the margins of the girdle. In her figures the anterior end of 

 the body is occupied ])y a large, yellow mass, which is usually though not always 

 present, and the nucleus is posteriorly placed. This large food mass ( 1) was 

 absent in our example with the nucleus anterior and the cytoplasm filled with 

 small spherules. These diiferences are not great enough to separate the two 

 forms. 



Comparisons. — This species shows the greatest extreme in the relative pro- 

 portions of epicone and liA-jjocone, the latter being comparatively minute. The 

 general tendency fi-om A)npJiidinium, with its relatively minute epicone, up 

 through Gijhinvdhiiam and G/jrodiitinDi, has been towards an equalization of 

 the two parts of the body with a slight leaning towards a greater size in the 

 h^i^ocone. These conditions are reversed in G. (/hiKcuni, as also to a much 

 smaller extent in G. rrassNDi (fig. CC, 21) and G. dorsmii (fig. CC, 19). 



Gyrodinium grave (Meunier) 

 Text figure DD, 7 

 Spirodinium grave Meunier (1010), p. 6-4, pi. U, figs. 27, 28. 



Diagnosis. — A small species with stout elliijsoidal body, its length 1.29 

 transdiameters ; girdle a descending left spiral, displaced 0.6 transdiameter, 

 constricting the body; sulcus extending from anterior end of girdle to near 

 antapex; surface finely striate. I^ength, 57/*. Arctic Ocean off Nova Zembla. 



Description. — Body stout ellipsoidal, with broadly rounded apices, widest in the middle, its 

 length 1.29 transdiameters at the widest part. The epicone and hypocone are subequal. The 

 epicone is subhemispherical in outline, with a length on the left and right sides of 0.24 and 0.7 

 respectively of the total length of the body. The hyi)ocone is broadly rounded with broad, 

 slightly fiattened antapex. 



The girdle in Meunier 's figure (1910, pi. U, fig. 27, reproduced in our text figure DD, 7) is 

 not complete in its proximal end. This has been completed in our figure by the slender lines. 

 It joins the sulcus at a distance from the apex of about 0.24 of the total length of the body. It 

 sweeps around the body in a descending left spiral of 1.25 turns, displaced posteriorly 0.6 trans- 

 diameter. It is wide, about 0.09 transdiameter. and deeply impressed with rounded borders. 

 The sulcus extends from the proximal to the distal end of the girdle. It probably has a longer 

 extension posteriorly at least. Flagella are lacking in the figures given. 



The nucleus is a large subsi)heroidal body found in the center of the organism. Its axis is 

 about 0.5 transdiameter in length. It is filled with coarse, chromatin strands. The surface is 



