kofoid: new species of dinoflagellates. 1G9 



toward the girdle, bifurcated near the apical pore, passing posteriorly 0.6 of the 

 distance to the antapex. 



Sutures marked by broad structureless intercalary bands. Epitheca -svitli 5 

 precingulars, and 1 apical which is deeply cleft by the longitudinal furrow 

 but appears to lack the dorsal median suture necessary to complete the divi- 

 sion into two plates. A minute accessory plate in the precingular series at the 

 left of the longitudinal furrow. Hypotheca with 5 postcingulars, 1 antapical, 

 and an accessory near the longitudinal furrow. The right ventral precingulur 

 and left ventral postcingular are small plates. 



Plates reticulate with characteristic reticulations similar to those of S.frag- 

 ilis, with quite regular arrangement in places. Scattered nodal pores in the 

 mesh and eccentric pores in each reticulation. 



Length, 165 fi; transdiameter, 115 /*. 



Station, 4728. 



PROTOCERATIUM (Bergh) Kofoid. 



The thecal plates of this genus have not hitherto been determined, as the 

 known species have lacked suture ridges and the density of the contents has 

 interfered with the determination of the tliecal structure. The following 

 species has the plates clearly defined, and the definition of the genus may be 

 accordingly emended. 



Thecal wall definitely divided into plates, epitheca with one hexagonal apical 

 plate and no apical pore, six nearly equal precingulars, the midventral one ad- 

 jacent to, or containing the anterior end of the longitudinal furrow; hypotheca 

 with six nearly equal postcingulars, the midventral one smaller and forming 

 the posterior part of the longitudinal furrow plate, and one large antapical. 



Protoceratium areolatum, sp. nov. 



Plate 12, Fig. 71. 



A minute species of ellipsoidal form. Thecal wall coarsely areolate, sutures 

 marked by heavy ribs. 



Body almost a perfect ellipsoid, the length 1.25 times the diameter in the 

 furrow, and nearly equalling the diameter on the lists of the girdle. Epitheca 

 less than the hypotheca by the width of the girdle, a low dome, abruptly flar- 

 ing into the wide list, its altitude 0.33 of the diameter on the lists. Midventral 

 plate slightly flattened, left side slightly wider than the right. 



Hypotheca hemispherical, midventral plate somewhat excavated. 



The girdle is wide, with wide, membranous, ribbed lists, furrow scarcely im- 

 pressed, forming a descending right spiral with displacement equalling its width. 

 Flagellar pore at proximal end of posterior list. Longitudinal furrow con- 

 fined to girdle and hypotheca, running back to antapical plate on the ventral 

 postcingular. 



Plates normal, suture lines marked by ridges somewhat heavier than those 



