kofoid: new species of dinoflagellates. 181 



apical plates. This salient angle is the most striking feature of the species. 

 The antapicals are short or more or less elongated, acute, and divergent. The 

 postindentation is deep or shallow, being 0.2-0.8 of a transdiameter (of hypo- 

 theca) in depth. The postmargin forms a broadly rounded or subacute bay, 

 with a hyaline irregularly toothed fin along most of the margin. 



Girdle slightly oblique, displaced a little less than its width, obsolete dis- 

 tally. Anterior ridge very heavy, posterior one scarcely developed. 



The plates are normal, the left intercalary being relatively large. The 

 sutures are marked by prominent ridges, or by broad bands with or without 

 tine reticulations. Thecal wall porulate, covered with reticulations of me- 

 dium size. About 20 contiguous to the posterior side of the girdle on the 

 dorsal side in the dorsal apical. Reticulation often lacking on some of the 

 plates. 



Chromatophores few, centrally located, spheroidal. Sometimes massed in 

 chromospheres. 



This is the most abundant species of the genus in tropical waters. It is 

 exceedingly variable, but the diverse forms are so well connected by interme- 

 diates that they must be regarded as one species. The following forms may be 

 recognized: — 



Forma typica (Plate 6, Fig. 37). With little constriction of epitheca, 

 moderate marginal projection of the left postcingulars and postindentation. 



Forma extrema (Plate 6, Fig. 38). With constricted epitheca and relatively 

 narrow hypotheca, excessive marginal projection and deep postindentation, and 

 considerable obliquity of the hypotheca. 



Forma mediocris (Plate 6, Fig. 39). With little deflection of hypotheca and 

 antapicals, less inequality in transdiameters, slight marginal projection, and 

 often with moderate subacute postindentation. 



Forma deformata (Plate 6, Fig. 40). With right or left antapical 

 undeveloped. 



Length, 118 to 170 /x; transdiameter of epitheca, 67 to 100 /x; of hypotheca, 

 48 to 91 ft. 



At various stations between 4594 and 4724. 



This species (forma extrema) is figured in Capt. R. F. Scott's " Voyage of the 

 Discovery," Vol. 2, on the plate facing p. 192 under the legend " Peridineans 

 caught on the voyage out." 



Heterodinium globosum, sp. nov. 



Plate 8, Fig. 51. 



A small species with, rotund body, short apical horn, and small spine-like 

 antapicals, deficient list, and sparse reticulations. 



The body is spheroidal, the length (excluding apical and antapical horns) 

 about equals the transverse and dorso-ventral diameter. The total length is 

 1.3 times the transdiameter and 1.5 times the dorso-ventral. The epitheca is 

 dome-shaped, flaring at the girdle, and constricted apically to a short, stout horn 



