352 University of California Publications. [ ZOOLOGY 
and the latter not deflected distally, both formed by sharp pro- 
jecting ridges of the theeal wall. Longitudinal furrow short, 
its length less than 0.5 distance to the postmargin, broad and 
shallow, its distal two-thirds enlarged. 
Theceal plates imperfectly known. Ventral plates of typical 
number and arrangement except that the right ventral post- 
median (16) is not continued to the postmargin but appears to 
be divided into postmedian and antapical moieties. Suture lines 
faint, bordered by smooth structureless zones. No prominent 
lateral ridges. No lists or spines. Thecal wall minutely and 
faintly reticulate with subregular polygons with centrally located 
pores. Polygons relatively very numerous. 
Plasma dense, heavily vacuolated, chromatophores irregular, 
peripherally located, greenish yellow; nucleus near flagellar pore, 
ellipsoidal. 
Dimensions :—leneth, 42; transdiameter, 391; width of fur- 
row, 4-5; diameter of polygons, 2-3». 
Taken once in vertical haul from 165 fathoms off San Diego 
in June. 
Although this organism does not have the deficient girdle 
found in other species of the genus its thecal plates, in so far 
as they are known, are those of Heterodinium. 
Heterodinium doma (Murr. et Whitt.). 
Peridinium doma Murray and Whitting (799), p. 327, Pl. 30, fig. 3. 
Plainly belongs to Heterodiniwm because of the clearly shown 
ventral pit in the central expansion of the median ventral suture. 
The plates are only partially shown but in the one view (ventral) 
given they conform to Heterodinium so far as shown. The girdle 
and furrows are also typical. 
The species is characterized by the spheroidal form, sub- 
median girdle, broadly rounded apex, entire absence of antap- 
icals, median reticulations of subregular polygons and somewhat 
salient suture ridges. 
Reported from the warm temperate Atlantie between 34°- 
Bo Ne 
