KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 247 



Description.^ — The body is rotund, broadl.y elliptical in ventral view, dorsoventrally com- 

 pressed, with broad, rounded apices, its length 1.26 transdiameters at the widest pai-t, its dorso- 

 veutral diameter about 0.S8 transdiameter. The hypoeone is slightly larger than the epicone, 

 its length being greater by 0.15. The epicone is hemispherical in ventral view with symmetrically 

 rounded sides. It has a length on the left and right sides of 0.33 and 0.48 respectively of the 

 total length of the body. Tlie liypocone also has the form of a slightly elongated hemisphere in 

 ventral view with smoothly rounded sides subparallel anteriorly. 



The girdle is slightly premedian in position, its proximal end joining the sulcus at a distance 

 from the apex of 0.33 and its distal end 0.48 respectively of the total length of the body. It 

 follows a descending left spiral course around the body, its distal end displaced posteriorly about 

 two widths of the girdle. The furrow is wide, about 0.08 transdiameter, and is shallow with 

 smooth borders. The sulcus invades the epicone but a short distance. It extends posteriorly on 

 the hypoeone in a straight line to near the antapex. 'The trough is wide and about 0.14 of the 

 dorsoventral diameter in depth. The anterior flagellar pore opens at the proximal junction of 

 the girdle and sulcus, the posterior pore at about 0.3 of the distance between the distal junction 

 and the antapex. 



The nucleus is a spheroidal body, found in the center of the organism. Its axis is about 0.43 

 transdiameter in length. The cytoplasm is granular and is arranged in radial strands, sur- 

 rounding oblong vacuoles which extend from near the nucleus to the periphery. In surface view 

 these vacuoles give tlie organism a coarsely vacuolate appearance, with alveoli varying in size. 

 The surface is striate, with fine, longitudinal lines, placed closely together and equal in number 

 on both epicone and hypoeone, and about fifty across the ventral face. 



Dimensions. — Length, 86/^ ; transdiameter, 19;^ ; dorsoventral diameter, 59m ; 

 axis of nucleus, 27;^. 



OcciTRREXCE. — A single individual was taken June 23, 1904, 13 miles off La 

 Jolla, California, with a No. 20 silk net, in a haul from 265 meters to the surface. 



Comparisons. — This is the most s\anmetrieally rotund species in the sub- 

 genus Pachydimu))!. It lacks entirely the manmiillated surface and any outer 

 alveolar layer, characteristic of that subgenus and, in consequence, might l)e 

 included in Lineadinium with other striate species. It has, however, the 

 rotundity of species of the former subgenus, combined with the marked radial 

 arrangement of the internal metaplasmic structures, so generally developed in 

 Pacliydinkim. It is the most finely striate species in the genus Gymnodinium. 



Gymnodinium ravenescens s}). nov. 



Plate 1, figure 10; text figure X, 21 



Diagnosis. — This is a small species with ellipsoidal body, its length 1.47 

 transdiameters; girdle premedian, displaced three times its own width; sulcus 

 extending from apex to antapex; olive ochre chromatophores. Length, 53^^. 

 Pacific off La Jolla, California, August. 



Description. — The body is symmetrically ellipsoidal with broad, rounded apices, its length 

 1.47 transdiameters at the widest part. A cross-section of the body is nearly circular with a 

 slight indentation on the midventral surface. The length of the hypoeone is greater than that 

 of the epicone by 0.27. Tlie transdiameters of both are .subequal. The epicone is hemispherical 

 anteriorly, the sides slightly elongated jjosteriorly. The apex is broad and rounded. It has a 

 length on the left and right sides of 0.31 and 0.49 respectively of the total length of the body. 



