103 



retains Cleve's specific name but assigns the species to the genus 

 Gonyaulax while Levander"^ cites the species as Ceratiwn (?) hyper- 

 horeum. 



The fullest account of this obscure form, thus far published, is 

 given by Paulsen" who discusses the synonomy in part and definitely 

 assigns the species to the genus Gonyaulax since the longitudinal furrow 

 reaches the apical pore and there is but a single antapical plate. He 

 gives a ventral, lateral, antapical and a partial dorsal view of the theca 

 but unfortunately his figures fail to give in any case all of the plates. 

 Those of the epitheca are left quite incomplete, and on the ventral face 

 of the hypotheca they are differently represented in his figures a and c. 

 As thus figured by Paulsen the ventral face of this organism bears a 

 striking resemblance to that found in species of the genus Heterodinium^ 

 in its mid ventral extension of the much narrowed longitudinal furrow 

 upon the epitheca to the apical pore and in the median deflection of this 

 furrow to the left, in the widened posterior end of the furrow, in the 

 posterior deflection of the distal end of the posterior list of the girdle 

 and its connection with the divergent suture line on the right face of 

 the hypotheca, and in the reticulated wall of the theca. These resem- 

 blances led me s in the absence of knowledge of its plates, to suggest the 

 inclusion of G, triacanilia in the newly established genus, Heterodinium. 



Since the publication of this paper I have fortunately had the oppor- 

 tunity to examine this rare species in some collections from Alaska made 

 by the U. S. Str. Albatross in the summer of 1905. In one collection 

 made at Loring (55° 40' N, 133° 35' W), Sept. 15, there is a considerable 

 number of Gonyaulax triacantJm, including some empty loricae, upon 

 which the thecal structure can be determined fully and accurately. I am 

 indebted to Hon. Geo. M. Bowers, Commisioner of the U. S. Bureau 

 of Fisheries, for this material and permission to publish this note upon it. 



The accompanying figures indicate the number and arrangment of 

 the plates which are unquestionably those of Gonyaulax., as follows: 

 there are three tapering apicals, [1 — 5), five praecingulars , [4 — 8), the 

 girdle plate, five postcingulars, one cuneate accessory [14] at the left of 

 the longitudinal furrow plate of the hypotheca, a single antapical (iôj, 

 and the longitudinal forrow plate {16). In one specimen I was able to 

 distinguish a minute accessory plate in the epitheca near the midventral 

 line anterior to the girdle at the left of the longitudinal furrow. 



6 ibid. p. 148. 



7 1. c. p. 21, 22, fig 5. 



8 Kofoid, C. A., J'i'«o/'/(75'e//«te of the San Diego region. I. On Heterodinium, 

 a new genus of the Peridinidae. Univ. of Calif. Pubs. Zool. Vol. II, No. 8. p. 341 

 -368, Pis. 17-19. 1906. 



