No. 6. — Reports on the Scientific Results of the Expedition to 

 the Eastern Tropical Pacific, in charge of Alexander Agassiz, 

 by the U. S. Fish Commission Steamer " Albatross" from 

 October, 1904, to March, 1905, Lieut. Commander L. M. 

 Garrett, U. S. N., commanding, 



IX. 



New Species of Dinoflagellates. By Charles 

 Atwood Kofoid. 



The pelagic collections of the Expedition made with the fine silk nets, 

 especially those made at the depth of 300 fms. and brought to the sur- 

 face in the open net, have contained a considerable number of species 

 of Dinoflagellates which are as yet undescribed. Pending the publica- 

 tion of the final report with full illustrations, the following brief de- 

 scriptions, accompanied by simple figures, are published of the new forms 

 for which the plates are in preparation. 



No attempt is made in these descriptions to discuss morphological 

 or systematic problems, nor to indicate or discuss the distribution of 

 the forms described. Nor is any list of the species found given here- 

 with, since practically all known species of this group have occurred in 

 the collections. 



Noteworthy among the forms here described is the considerable 

 number of new species of Amphisolenia, Heterodinium, Ceratium, 

 and Oxytoxum. There is also included a new genus, Acanthodinium, 

 which throws some light on the relationships of the problematical 

 organism Cladopyxis, linking it with little doubt near to the Ceratiidae 

 in the system. A unique new genus, Centrodinium, is represented by 

 three species, and Murrayella, related to Oxytoxum, including four 

 species, is also new. The plates of the obscure aud puzzling genus 

 Protoceratium are defined for the first time, and three species are added 

 to the highly phosphorescent genus Pyrocystis. The discovery of a new 

 representative of Ptychodiscus, a genus not reported since its description 

 by Stein in 1883, is recorded. 



In all three new genera, eighty-four new species, nine new " forms " 

 are described. Unless otherwise stated they are all from collections 



