1911] Kofoid: The Genus Gonyaulax. 221 



Comparisons: This species is a member of the G. spinifera 

 group, rehited to G. digifale (Pouehet), differing from it in its 

 size, in its more pronounced rotundity, its broad intercalary 

 bands, and in having few pores located sparingly in the nodes 

 of the fine reticulum instead of many centrally located in the 

 openings of the mesh, and in three finned antapical spines, 

 whereas G. spinifera usually has two spines, without fins. It 

 differs from G. spinifera in much greater size, less overhang of 

 girdle, and absence of expansion of longitudinal furrow opposite 

 the distal end of the girdle. 



Distribution : In neritie plankton of spring and summer at 

 San Diego. Less abundant in oceanic plankton. Many empty 

 thecae were taken in plankton off kelp zone in 1904 with Gonijau- 

 lax spinifera, G. polyeelra, Dinophijsis homunculns and Ceraiium 

 pentago)imn. The abundance of empty thecae in this region may 

 be due to the discharge of skeletons in faeces of the abundant 

 sessile plankton-feeding fauna of the kelp zone, or to adverse 

 local conditions about this zone leading to ecdysis. 



5. Gonyaulax triacantha Jorgensen 



PI. 11, figs. 11-1.5. 



Gonyaulax( ? ) triacantha Jorgensen (1899), no. 6, p. 35. 



Ceratium( ? ) hyyerhoreum Cleve (1900a), 1, pp. 14-1.5, pi. 18, fig. 14. 



Ceratium( ? ) hyperboreum Cleve (1901a), p. 223. 



Gonyaulax hyperborea (Cleve) Paulsen (1903), p. 90. 



Gonyaulax triacantha, Paulson (1904), pp. 21-22, fig. 5a-d. 



Heterodinium triacantha (Jorg.) Kofoid (1906a), p. 354. 



Gonyaulax triacantha, Kofoid (1906b), pp. 102-105, figs. 1-3. 



Ceratium hyperboreum, Lemmermann (1907), p. 298. 



Geratium hyperboreum, Linko (1907), p. 91. 



Amylax lata Meunier (1910), pp. 51-52", pi. 3, figs. 24-27. 

 Diagnosis: A small species (SO/a) with rotund hypotheca, 

 epitheca with concave faces, and obliquely truncated apex. 

 Girdle slightly displaced, ventral area spreading posteriorly to 

 the right, five to seven spreading antapical spines, surface finely 

 reticulate. Northern neritie species. 



Description : Body rotund posteriorly, concave anteriorly, flattened 

 ventrally, girdle postmedian. The length (excluding spines) 1.16 to 

 1.20 transdiametei's, dorso-ventral diameter 0.5 to 0.6 transdiameter, 

 girdle section reniform (pi. 11, figs. 11, 12) of empty thecae. The usual 

 form is more rotund (see Paulson, 1904, fig. 5d). Epitheca flaring at the 



