MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 107 



VI, DINOFLAGELLATE CYSTS WITH GON YA ULA X — TYPE TABULATION 



By W. A. S. SARJEANT 



INTRODUCTION 



The dinoflagellate genus Gonyaulax was originally proposed by Diesing (1866) in 

 the following terms : 



" Animalcula solitaria libra symmetrica. Corpus immutabile, ovatum, 

 ecaudatum, ciliatum, lorica, tabulata, sulco, hiante transversali in pagina 

 dorsali obliquo in pagina ventrali bis geniculato et altera longitudinali, ab 

 anfracto anteriori sulci transversalis ad extremitiatum anticam excurrenti, 

 tripartita inclusum cilii e sulcis prominentibus. Os terminale. Flagellum 

 unum pone os. Anus .... Ocellus nullus. Partitio ignota. Mariolae." 



The type species selected was G. spinifera (Claperide). An amended and much 

 fuller diagnosis was subsequently proposed by Kofoid (191 1) : 



" Body variously shaped, spheroidal, polyhedral, broadly fusiform, elongated 

 with stout apical and antapical prolongations, or dorsoventrally flattened. 

 Apex rounded or truncate symmetrically or asymmetrically, never acutely 

 symmetrically pointed. Antapex rounded, flattened, or pointed symmetrically 

 or asymmetrically. Girdle usually equatorial, descending, displaced distally 

 one to seven times its own width, and sometimes with slight overhang. Trans- 

 verse furrow impressed or not ; longitudinal furrow usually slightly indenting 

 the epitheca, often flaring distally, well developed, reaching to or approaching 

 the anatpex. Thecal wall consisting of one to six apical plates (i'-6'), none to 

 three anterior intercalaries (ia-3a), six precingulars (i"-6"), six girdle plates 

 (ig-6g), six postcingulars (i'"-6'"), one posterior intercalary (ip) and one 

 antapical (1""). The longitudinal furrow occupies the whole of the ventral area, 

 which slightly indents the epitheca and consists of one anterior, about four 

 intermediate, and one posterior plate. The midventral plate (1') of the apical 

 series is usually a narrow plate extending posteriorly to a junction with the 

 anterior plate of the ventral area, thus parting precingulars 1" and 6". When 

 guarded by lateral ridges it simulates an anterior extension of the longitudinal 

 furrow. It bears at its apex a delicate extension, the closing platelet which 

 cover the apical region. 



Surface smooth or rugose with major thickenings along suture lines and minor 

 ones on plates forming a regular or irregular polygonal mesh of varying size, often 

 with vermiculate longitudinal elements predominating, sometimes spinulate. 

 Furrows with or without lists which in many species are ribbed or spinulate. 

 One or more antapical spines sometimes present, rarely with sheathed spines of 

 the Ceratocorys type. Plates porulate, with pores in centres, angles or nodes of 

 the mesh. A peculiar large ventral pore occurs to the right of the midventral 

 line, usually near the suture between apical 1' and the plate to its right. Theca 

 divided obliquely in fission. Ecdysis frequently seen. Chromatophores yellow 

 to dark brown, often dense. In fresh, brackish and marine waters from boreal 

 to tropical regions." 



