330 University of California Publications in Zoology [Vol. 19 



4. The girdle has hitherto been overlooked. It is a shallow trough 

 at the left of the sulcus and at right angles to it. It is seen best in 

 small individuals. 



5. The longitudinal flagellum is l'edueed and lies within the oral 

 pouch. The transverse flagellum is represented by the prehensile tooth 

 at the proximal end of the girdle at the left of the base of the longi- 

 tudinal flagellum. This organ exhibits structural undulations, and 

 spasmodic or rhythmical contractions. 



6. Distention by hydrostatic vacuoles, with flotation replacing 

 active locomotion, has led to degeneration of the flagella and their 

 reduction in size, and to the almost complete disappearance of the 

 girdle. 



7. Noctiluca belongs in the Noctilucidae, a family of the tribe 

 Gymnodinioidae, with Pavillardia, another tentaculate, naked, non- 

 ocellate dinoflagellate. 



8. There is no morphological justification of a separate order of 

 flagellates to hold Noctiluca, such as the Cystoflagellata Haeckel. 



9. The Cystoflagellata may be retained as thus emended to receive 

 Leptodiscus and Craspedotella pending discovery of their affinities. 



Transmitted December 2i, 1919. 



Zoological Laboratory, University op California, 

 Berkeley, California. 





