358 University of California Publications. | ZooLoGy 
Heterodinium leiorhynchum (Murr. et Whitt.). 
Peridinium leiorhynchum Murray and Whitting (799), pp. 326-327, Pl. 29, 
figs. 2a, b. 
This is unquestionably a Heterodinium as it shows a mid- 
ventral pit upon the epitheca, the doubled lateral sutures and 
diminishing posterior list of the transverse furrow. The plates 
are very imperfectly shown though there is a suggestion of the 
left intercalary of the epitheca in the sight shoulder on the left 
epithecal margin, and in the incomplete suture lines of the latera! 
view. 
The species is characterized by the somewhat differentiated 
apical horn, the unequal, pointed, divergent antapicals termi- 
nating in spines, the rotundity at the girdle, prominent suture 
ridges (incomplete in figure), smooth or coarsely reticulate theeal 
wall, and fenestrated lists of the girdle. 
Reported from the warm temperate Atlantie from 20°—40° N. 
Heterodinium blackmani (Murr. et. Whitt.). 
Peridinium Blackmani Murray and Whitting (’99), pp. 327-328, Pl. 29, 
figs. 6a, b, ¢. 
This superb and clearly marked species is the only one in 
which the left intercalary plate is shown by Murray and Whit- 
ting (99). It is unquestionably a typical Heterodiniwm though 
these authors fail to show the ventral plates of the epitheca and 
the ventral pit characteristic of the genus. The remainder of 
the plates is almost completely shown. The prominent doubled 
lateral sutures, the short longitudinal furrow, and the poste- 
riorly deflected posterior list of the transverse furrow stamp this 
species as a typical Heterodiniwm. 
The species is characterized by the curved epitheca flaring 
to the greatly expanded equator, submedian girdle, divergent 
pointed antapicals. The suture lines are marked by prominent 
lists and the plates are reticulate with delicate subregular hex- 
agonal polygons, which exhibit a tendency to horizontal elonga- 
tion on the epitheca. 
Reported from the Caribbean Sea and tropical Atlantic from 
9°-25° N. 
