292 MEMOIRS OF THE UNIVERSITY OP CALIFORNIA 



CoMPAEisoxs. — Gyrodinmm, contortum, in its wide displacement of the gii'dle 

 and its overhang, resulting from the torsion of the siilcus. leads onward in the 

 line of evolution to the next genus, CochJodinium. The torsion of the intereing- 

 ular part of the sulcus in this species is greater than in G. ochraceum sp. no v. 

 (fig. DD. 17), though without the antapical loop of that species, which gives 

 its entire sulcus a slightly greater torsion than in G. contortion. It belongs in 

 this group of ochraceous striate species, including G. ochraceum sp. nov. and 

 G. fith-tini sp. nov. (figs. DD, 9, 17), all of which appear to lack chromatophores. 

 It is clearly distinguishable from these by its proportions. 



Gyrodinium corallinum sp. nov. 



Plate 10, figure 117 ; test figure DD, 12 



DiAGxosis. — A large species with as^inmetrically biconical body, its lengih 

 1.96 transdiameters ; girdle a premedian, descending left spiral, displaced 0.62 

 transdiameter ; sulcus extends from gii'dle or near apex to antapex; surface 

 moderately striate; color, greenish yellow with scattered coral-red pigment. 

 Length, 155ii*. Pacific off La Jolla, California, July. 



Description. — The body is asymmetrically biconieal, nearly subrhomboidal in shape, its 

 longest transdiameter slightly premedian, its length 1.96 transdiameters at the widest part. A 

 cross-section of the body is nearly circular. The hypocone far exceeds the epicone in size, its 

 length being greater by 0.21 of its own length. The epieone has the shape of a broad cone of 

 about 70° with blunt apex. It has a length on the left and right sides of 0.26 and 0.59 respec- 

 tively of the total length of the body. The sides of the epicone are nearly straight or sometimes 

 slightly concave on the right side. The hypocone is elongate conical, of about 40°. with sides 

 somewhat more convex than those of the epicone. It has a length on the left and right sides of 

 the body of 0.72 and 0.42 respectively of the total length of the body. The blunt antapex is 

 slightly wider and more rotund than the apex. 



The girdle is premedian in position for the greater part of its length. Its proximal end joins 

 the sulcus at a distance from the apex of 0.26 of the total length of the body. It follows a 

 descending left spiral course around the bod.y, the first 0.5 transdiameter of which is nearly in 

 a transverse direction, gradually steepening onward until it joins the sulcus at a distance from 

 the apex of 0.59 of the total length of the body, and at an angle of about 55° with the longi- 

 tudinal plane of the body. Its distal end is displaced posteriorly about 0.62 transdiameter. The 

 furrow has a width of about 0.06 transdiameter, and is deeply impressed with smooth borders. 

 The sulcus begins near the apex and extends posteriorly in an almost straight line to the antapex. 

 On the epicone it is narrow almost to invisibility in some individuals. In others, particularly 

 those having food masses present, it is wider, showing the evident correlation of the sulcal area 

 and food ingestion. The anterior flagellar pore is found at the anterior junction of the girdle 

 and sulcus, the posterior pore midway between the posterior junction and the antapex. 



The nucleus is lai-ge, spherical and slightlj- premedian in position. It is differentiated into 

 two distinct parts. The outer, circular zone, which is about 0.1 of the total transdiameter of 

 the nucleus in width, is composed of pinkish vacuoles, elongated in optical section with the long 

 axis at right angles to the surface of the nucleus. Outside of these is a clear, double-contoured 

 membrane. The inner zone is apparently separated from the alveolar layer by a membrane or 

 a very thin, clear area. The central area is completely filled with chromatin granules without 

 evident linear arrangement. The axis of the nucleus is about 0.47 transdiameter in length. 



