kofoid and michener: dinoflagellates. 269 



Amphitholidae. 



74. Amphitholus quincuncialis Kofoid 



Incertae sedis. 



75. Berghiella perplexa 



Gonyaulax Diesing. 



The plates in this genus are an apical series of three to six plates (l'-3' to 6'), 

 an incomplete series of anterior intercalaries (0 a -4°), six precingulars (l"-6"), 

 six girdle plates (1-6), six postcingulars (l'"-6'"), one posterior intercalary 

 (l p ), and one antapical (1"")- 



Subgenus Fusigonyaulax Kofoid. 

 The acuta group. 

 Biconical species with apical and antapical horns. 



Gonyaulax acuta, sp. nov. 



A large biconical species resembling G. expansa, sp. nov., but differing from 

 it in size, form of ventral area and antapical horn, and in surface markings. 

 Length nearly 2 transdiameters, midbody rounded; epitheca abruptly con- 

 tracted to truncate apical horn, ant apex more tapering, acuminate, nearly 

 symmetrical. Girdle descending, displaced 1.5 girdle widths. Ventral area 

 very narrow throughout, deeply indenting epitheca, not widely flaring poste- 

 riorly, terminating asymmetrically on right postmargin. Ventral pore on 

 apical 3'. Plate formula 3', 0", 6", 6, 6'", 1", 1"". Apical 1' slender; pre- 

 cingular 6" quadrangular; postcingular V" minute, squarish; posterior 

 intercalary l p elongated, carried out on antapical horn; antapical 1"" forming 

 stout antapical spine, most exposed dorsally. Surface areolate with few 

 linear riblets, sparsely porulate. 



Length, 100 n; transdiameter, 48 //. 



Sta. 4719. 



Gonyaulax expansa, sp. nov. 



A medium sized biconical species flaring widely at the girdle, resembling 

 Spiraulax jolliffei (Murr. and Whitt.) in form. Length 1.7 transdiameters. 

 Epitheca abruptly contracted to a tapering, truncate, apical horn. Antapex 

 acuminate, asymmetrical. Girdle descending, displaced 2 girdle widths. 



