kofoid: new species of dinoflagellates. 177 



Heterodinium agassizi, sp. nor. 



Plate 6, Fig. 35. 



A small species with very broadly rounded apex, scoop-shaped epitheca, and 

 subequal antapicals. The bifurcation is deep and evenly rounded. The retic- 

 ulations are of medium size and fairly regular. 



The epitheca is broad, its apex almost a semicircle, with a slight constriction 

 some distance in front of the girdle but not so deep as in H. fides. Ventral 

 surface concave. Altitude of epitheca on ventral face 1.16 times the transdi- 

 ameter at the girdle, on the dorsal 0.82 times. Ventral area elongated, pit at 

 its anterior end. 



Hypotheca about equal to the epitheca. Its lateral margins nearly straight, 

 convergent, distance between the tips of the antapicals a little less than 0.5 of a 

 transdiameter. Postindentation deep, axial depth about 0.5 of a transdiameter, 

 evenly rounded. Antapicals subequal, acute, scarcely spreading. Ventral face 

 deeply impressed about the longitudinal furrow. Girdle narrow, oblique, dis- 

 placed its own width, coarsely reticulate ; not deeply impressed, ridges low. 



Thecal wall reticulate with polygons of medium size, which are subregular 

 along the margins. Reticulations porulate. Marginal sutures very heavy. 

 Below the girdle on the dorsal side there are 34 contiguous reticulations and 

 about 130 in the dorsal apical plate. Plates normal, obscure on ventral face 

 of hypotheca. 



Chromatophores bright cadmium yellow. 



Length, 155 fi ; transdiameter, 78 it. 



Station, 4699. 



Heterodinium calvum, sp. nov. 



Plate 7, Fig. 43. 



A large spheroidal species with wide girdle and smooth wall. 



Body spheroidal, flattened a little on the ventral face. Epitheca hemisphe- 

 roidal, with rounded apex, flaring a little at the girdle. The ventral pit is 

 median, in a quadrangular ventral area. The hypotheca is also hemispheroidal, 

 with flattened antapex, with angular outline. It is excavated ventrally. The 

 girdle is median, is very wide, especially in the distal half. The transverse 

 furrow is impressed and the anterior ridge has considerable overhang. It 

 forms a descending right spiral displaced its own width. The longitudinal 

 furrow is slender, narrow, and extends but little beyond the posterior list of 

 the distal end of the girdle. 



The thecal wall is smooth, suture lines faintly marked, or with low ridges 

 spinous in places, on the ventral face of the hypotheca. Porulate, but with- 

 out other surface modification. 



Length, 75 /a ; transdiameter, 75 ft. 



Station, 4739. 

 vol. l. — No. 6 12 



