282 bulletin: museum of comparative zoology. 



Peridinium karsteni, sp. nov. 



A large species resembling P. multistriatum Kofoid (1907), pi. 30, figs. 40, 41, 

 but differing in proportions and in form of the girdle. Body widely expanded 

 at girdle, rounded pentagonal in ventral view with concave antapex and very 

 short, acute antapical horns, the right slightly longer. Apex inclined ventrally. 

 Epitheca a little less than hypotheca, its dorsal altitude 0.4 transdiameter, 

 contracted distally to a small, short, apical horn. Hypotheca broadly rounded 

 to region of short antapical horns. Distance between their tips 0.3 transdiam- 

 eter, length of right 1 and of left 1.5 girdle widths. Postmargin irregularly 

 concave, but the arc very shallow. Girdle descending, displaced 4 girdle 

 widths, the proximal end ascending in a very abrupt curve, and the distal 

 descending in a sweeping one from the right margin. Furrow impressed, with 

 low ribbed lists. Ventral area 3 girdle widths wide, expanding just behind 

 distal end of girdle, reaching postmargin. Three dorsal intercalary plates. 

 Apical 1', the rhomb plate, 3.5 girdle widths across. Ventral notch 2 girdle 

 widths long. Surface with very wide, striate, intercalary bands and reduced 

 reticulate-porulate areas of plates as in P. multistriatum. Width of dorsal 

 postcingular band 0.27 transdiameter. 



Length, 55 ^; transdiameter, 60 ll. 



Sta. 4670. 



Peridinium nodulosum, sp. nov. 



A small spheroidal species with minute apical horn, ascending girdle without 

 overhang, and surface with scattered nodular elevations. Differs from P. 

 globulus Stein in wider girdle without proximal curvature, and from P. quar- 

 nerense (Br. Schroder) Broch, in absence of overhang and less displacement 

 of girdle, and from both in the surface markings. Body almost spheroidal. 

 Length, excluding horn and spines, 1.05 transdiameters. Girdle section 

 circular, with little ventral flattening on hypotheca. Epitheca equals hypo- 

 theca, both hemispherical. Apical horn minute, 0.4 girdle width across, 

 and less in height. Ventral notch minute. Girdle ascending, without proxi- 

 mal or distal curvature, displaced 1 girdle width, with feeble marginal ridges, 

 and very low (0.2 girdle width) hyaline fin. Ventral area curved, narrow, 

 flagellar pore posteriorly located. Two antapical spines on postmargin of 

 ventral area each 1.2 girdle widths in length, the right more distal in origin, 

 both finned. The right side of ventral area with long low fin. Three dorsal 

 intercalaries. Apical V very broad, in contact with both precingular 1" 

 and 6". Surface with scattered elevated nodules of irregular shape. 



Length, of midbody, 42 it, total 49 n) transdiameter, 38 fx. 



Sta. 4706. 



