VoL. 2] Kofoid—On Heterodinium. 359 
shaped, compressed dorso-ventrally, its altitude (ventral) is 0.7 
transdiameter. No apical horn is differentiated and though com- 
pressed dorso-ventrally it is not thinned down to a sharp edge 
at the doubled lateral sutures. The ventral face is scarcely ex- 
eavated. The broad midventral suture runs from the longi- 
tudinal furrow to the apical pore swerving towards the left at 
the ventral pit. 
The hypotheea is rotund, its altitude (mid-dorsal) 0.6 trans- 
diameter. The antapicals are very unequal, the right is about 
one-half the length of the left and is abruptly imcurved to an 
acute tip. The left is not incurved and is somewhat tapering. 
Its length is 0.3 transdiameter. The postmargin between the 
antapicals is slighly concave and is 0.4 transdiameter in length. 
The plates are typical in number, the left intercalary being 
confined to the dorsal face. The dorsal premedians are very 
low, scarcely exceeding the girdle in width. The dorsal post- 
medians on the other hand are unusually long, and the posterior 
angle of the right one projects slightly beyond the margin. 
The girdle is narrow and slightly oblique (15° postero-ven- 
trally) to the equatorial plane. The transverse furrow is postero- 
dexiotropie with a displacement of its own width. It is scarcely 
indented, the thecal wall forming a slight anterior ridge, and 
a small posterior one which fades into the right antapical suture 
distally. The longitudinal furrow is narrow and short, 0.6 dis- 
tance to postmargin. 
The theeal wall is structureless save for scattered pores in 
the two individuals thus far observed. These may both be young 
stages and the older ones may be reticulate as are other species 
in the genus, but there is not the slightest evidence of reticula- 
tions on the thecal walls of these two individuals. The suture 
lines are light and faint. The midventral one on the epitheca 
is broad in the posterior half between the ventral pit and the 
flagellar pore, and the lateral sutures of the epitheca and hy- 
potheca are doubled and prominent. The right dorsal premedian 
suture is very oblique. No fins or lists were noted. 
The plasma is coarsely granular, chromatophores few, large, 
spheroidal, clustered near the center. 
