KOFOID AND MICHENER: DINOFLAGELLATES. 287 



Centrodinium porulosa, sp. nov. 



An elongated, abundantly porulate species of small size, with little distal 

 asymmetry, approaching Murrayella in some respects. Body elongated, 

 laterally compressed, with blunt, squarish apex and pointed curved antapex. 

 Length 3.3 transdiameters. Girdle section elliptical with longer axis dorso- 

 ventral. Epitheca less than hypotheca, its length 1.45 transdiameters, 

 conical with truncate apex in ventral view, asymmetrical in lateral view, with 

 apex deflected ventrally. Apex bluntly rounded, 1 girdle width in dorso- 

 ventral and 0.8 in transverse diameter. Hypotheca tapering, asymmetrically 

 conical in both lateral and ventral view, the acute antapex slightly deflected 

 ventrally and to the left. Girdle premedian, displaced 0.45 girdle width, 

 narrowed a little distally, not deeply impressed, with heavy marginal ridge 

 but no lists. Ventral area tapering, less than a girdle width across, extending 

 5 girdle widths beyond girdle. Surface abundantly porulate with coarse 

 pores, with interspersed areoles. Faint lines along sutures. 



Length, 70 n; transdiameter, 20 /x; dorso-ventral diameter, 23 n. 



Sta. 4729. 



OXYTOXTJM BREVE, Sp. nOV. 



A minute species of the 0. sphaeroideum group somewhat resembling Stein's 

 fig. 13, (1883), pi. 5. It differs from it, however, in proportions, and in ab- 

 sence of any trough-like depression in the girdle region. Body broadly ovoidal 

 with projecting epitheca and acute apices. Length 1.4 times greatest trans- 

 diameter which is located some distance behind the girdle. Epitheca a minute 

 pointed dome, 0.4 greatest transdiameter in greatest altitude, and 0.5 in 

 greatest basal transdiameter. Hypotheca globular, with pointed antapex, 

 its transdiameter at posterior margin of girdle 0.8 of greatest transdiameter 

 which is 0.57 of total length from apex. Girdle descending, narrowing distally 

 to 0.8 its initial width, very slightly displaced, not impressed or marked in 

 any way by ridges or lists, merely the sloping shoulder of girdle plates whose 

 vertical extent nearly equals that of the superposed but smaller epitheca. 

 Ventral area reduced to a minute notch in hypotheca. Surface smooth. 



Length, 20 y.; transdiameter, greatest, 14 n, at posterior edge of girdle, 11 n. 



Sta. 4733. 



OXYTOXUM CURVATUM (Kofoid). 



Described by Kofoid (1907), pi. 1, figs. 1, 2, as Prorocentrum curvatum. An 

 analysis of its plates shows that it is a peculiar Oxytoxum with its epitheca 

 reduced to a mere terminal button and the girdle to a surrounding shelf, 

 without any anterior list or rib. The flagellar pore and ventral area which 

 is very small, are on the concave face. The ventral area is scarcely deeper 

 than the width of the small apex. 



