KOFOID AND SWEZY: UN ARMORED DINOPLAGELLATA 353 



The erirdle meets the sulcus at a distance from the apex at its proximal and distal ends of 

 0.28 and 0.82 respectively of the total length of the body. It sweeps around the body at an 

 angle of about 30° witli the transverse plane, forming a descending left spiral of two turns, 

 joining the sulcus at a distance from the antapex of 0.16 of the total length of the body with a 

 displacement of 1.5 transdiameters. The furrow has a width of about 0.08 transdiameter and 

 is deeply impressed, undercutting the anterior border and curving gradually to the posterior 

 one. The borders are smooth and rounded. The .sulcus invades the epicone for a short distance 

 anterior to its proximal junction with the sulcus. It sweeps po.steriorly in a descending left 

 spiral which forms an angle of about 50° with the transverse plane in the first part of its course, 

 gradually changing in the latter part of its course to about 30°. The furrow is about half the 

 width of the girdle for the first half of its length, becoming narrower distally and enlarging 

 again posterior to the distal junction with the girdle. It is deeply impressed with roimded 

 sides. Posterior to the distal junction it makes a loop of nearly 0.6 turn, termiiuiting at the 

 right side of the antapex on the dorsal side of the body. The anterior flagellar pore is located 

 at the anterior junction of the girdle and sulcus, the posterior pore a short distance beyond the 

 distal junction on the same side of the body. 



The nucleus is an ellipsoidal body posterocentrally located, its long axis slightly oblique to 

 the transverse plane of the body. Its major and minor axes are 0.64 and 0.35 transdiameter in 

 length respectively. 



Pusules were not present in the individual figured. The cytoplasm is coarsely granular and 

 is nearly filled with large ellipsoidal and spheroidal bodies and vacuoles of a clear, pale grey 

 color. Near the equatorial region were some smaller green oil globules and scattered over the 

 surface were minute blue-green droplets and mingled with them short green rodlets. In addition 

 a large, rounded, ochraceous-orange food mass was located near the anterior pore. Its cyto- 

 plasmic inclusions are evidences of a holozoic mode of nutrition. The color has for its back- 

 ground a pearl grey which is almost clear at the apex and elsewhere is thickly beset with minute 

 ochraceous-orange granules, or dots. These last are numerous near the surface and at the 

 antapex. Along the margin of the girdle and sulcus are large pigment masses varying in size 

 and black in color. From the middle region of the body a few rows, four to a semicircle, of 

 small rod -shaped melanin granules extend to the girdle at the left of the sulcus, and at the right 

 of it to nearly midway between the anterior pore and the apex. No striae or other surface 

 markings could be detected, though the linear arrangement of the small melanin granules suggests 

 a fundamental linear organization of the superficial cytoplasm. 



Dimensions. — Length, 183-185/*; transdiameter, 72/*; axes of nucleus, 45t^ 

 and 23/*; length of longitudinal flagellum, 45/*. The figure given of this species 

 (pi. 7, fig. 71) is the only one in our plates whicli shows the longitudinal flagel- 

 lum in any species with its full length. 



Occurrence. — Two individuals were taken on July 20, 1917, with a No. 25 

 silk net 6 miles off La Jolla, California, in a haul from 80 meters to the surface 

 and in a surface temperature of 20?5 C. 



CoMr.ARisoNS. — This is one of the largest species of the genus CochlodiiiiiDu, 

 being exceeded in size only by C. stmnguldtum (fig. GG, 8) with a length of 210/*. 

 It is the only species in the genus showing the presence of melanin and the 

 second species in all of the genera below Poiichetia, the other being Gijrodinium 

 spumantia (pi. 7, fig. 72). 



C. atromaculatum belongs in the citron group of the subgenus Cofhlod'uunm, 

 and differs from the remainder of the group mainly in the greater elongation 

 (pf the !»()(ly and in the presence of an antai)ical loo]), the latter feature fore- 

 shadowing the condition in the higher genus Pouchetia. 



