1911] Kofoid: The Genus Gomjaulax. 223 



length of longest spine 12 to 15/^; width of furrow, 4/a; Paulsen 

 (1908) gives length (without spine 1) as 72 to 84//,. Cleve's 

 (1900) figure is 70/x without spines. Alaskan specimens appear 

 to be smaller than those of European waters. 



Variation : This species varies in the number of spines. 

 Five can usually be found, and as many as seven sometimes 

 appear. The surface marking.s are more pronounced in some 

 individuals than in others and linear striae are sometimes more 

 evident than in the individual figured (pi. 11, fig. 13). Post- 

 cingular 1'" is subject to considerable variation in length. 



Comparisons: Gomjaulax triacaniha is one of the best defined 

 and most isolated species in the genus. It is remarkable both in 

 form and in the development of the antapical spines as well as 

 in the character of the surface markings. It is not structurally 

 nearly related to any other species and its inclusion in the spini- 

 fera group is justified mainly on the ground of its antapical 

 spines. Two dorsal intercalaries still further distinguish it. 



Synonomy : First described but without figures by Jorgensen 

 (1899) who questionably referred it to the genus Gomjaulax and 

 later by Cleve (1900) as Ceratium hijperhoreum. It was first 

 figured by Paulsen (1904) who analysed the plates incompletely 

 but verified Jorgensen 's conjecture that it belonged in Gonyau- 

 lax. It was' later referred by me (1906a) to my new genus 

 Heterodinium on account of certain structural features found in 

 Paulsen's incomplete figures, but this error on my part was cor- 

 rected a few months later (1906b) upon examination of material 

 from Alaska, which enabled me to extend the analysis of the 

 thecal plates. A fuller knowledge of the genus enables me in 

 the present paper to correct and supplement certain interpreta- 

 tions and deficiences in my earlier analysis. These are the cor- 

 rect analysis of the apical region showing 3 apicals (i', 2', 3') 

 and two dorsal intercalaries {1", 2") instead of 3 apicals (Kofoid, 

 1906b, fig. 1, pis. 1, 2, 3) ; six precingulars {l"-6") instead of 5 

 {4-8), and 6 postcingulars (l"'-6"'), instead of 5 {9-13). Paul- 

 sen's figure (1904, fig. 5a) was correct in suggesting the presence 

 of the small plate, my posteingular 1'", though it was not de- 

 limited therein from the posterior intercalary. 



