KOFOID AND MICHENER: DINOFLAGELLATES. 285 



obliquely posteriorly to the ventral face. Hypotheca scarcely contracted 

 to the horns, but slightly excavated ventrally. Antapical horns wide-set, 

 long, tapering, both curved to the left and ventrally, with points slightly 

 incurved, the left about twice the length of the right which may be as long as 

 0.4 transdiameter. Girdle scarcely displaced, with low anterior ridge and no 

 posterior one. Ventral area straight, very narrow, less than 0.5 girdle width 

 across and 0.28 transdiameter long. Surface with few scattered pores in 

 lines along sutures. 



Length, 155 mJ transdiameter, 92 n. 



Sta. 4739. 



Heterodinium lineatum, sp. nov. 



A bizarre form with elongated body and very large pores curiously elongated 

 in antero-posterior direction. Body ellipsoidal, its length 1.8 transdiameters 

 measured in the girdle. Girdle section circular. Epitheca equals hypotheca, 

 with convex, rounded sides and scarcely elevated apex. Hypotheca more 

 angular, longer on left side. Girdle median, descending, displaced less than 

 its width, posterior ridge deficient especially distally. Anterior ridge heavy, 

 salient. Ventral area expanding distally into a large pentagonal plate. Ven- 

 tral pore half way between apex and girdle, reniform, to right of bent mid- 

 ventral line. This species is peculiar in that the anterior intercalary plate 

 l a of the left shoulder is pushed forward to a minute contact with the apical 

 region and might thus be called an apical plate, in which series it would seem 

 to have a normal position. In all other particulars the species conforms to 

 well known Heterodinium characters and it therefore seems best to retain it 

 as an aberrant species of the genus. Sutures marked by heavy ridges (in 

 old thecae), pores in subregular horizontal rows, elongated to about twice 

 their width. Low lists on lateral apical sutures, lists about antapical plate 

 with spinules at nodes. 



Length, 60 m; transdiameter, in the girdle, 33 n, on anterior ridge, 40 n. 



Sta. 4701. 



Heterodinium minutum, sp. nov. 



A minute species of subspheroidal form, premedian, displaced, overhanging 

 girdle, two acicular antapical spines and smooth porulate surface. Body 

 subspheroidal, pot-shaped. Length equalling transdiameter on anterior 

 girdle ridge and on greater expansion of hypotheca. Epitheca less than 

 hypotheca, only 0.4 transdiameter in girdle in height, low dome-shaped, apex 

 not protruding save by its bounding ridge. Hypotheca with globular form 

 up to girdle but with equatorial expansion 0.33 of transdiameter in girdle 

 behind anterior girdle ridge. Girdle descending, displaced about 1.5 girdle 

 widths, with ends overhanging in midventral region 1 girdle width, distal 



