142 The Mastigophora 



athecate types with a girdle and sulcus; Peridinina, with a theca com- 

 posed of separate plates; Dinocapsina, with a dominant palmella and 

 a gymnodinioid flagellate stage; Dinococcina, in which the life-cycle may 

 include a dominant "pyrocystis" or crescent-cyst stage, a floating or at- 

 tached palmella, and a gymnodinioid flagellate stage. 



Fig. 4. 20. A. Gyrodinium melo Kofoid and Swezy, x475 (after K. & S.). 

 B. Gyrodinium submarinum Kofoid and Swezy, x425 (after K. & S.). C. 

 Torodinium teredo Kofoid and Swezy, x300 (after K. & S.). D. Gymnodi- 

 nium dissimile Kofoid and Swezy, x475 (after K. & S.). E. Amphidinium 

 dentatum Kofoid and Swezy, x575 (after K. & S.). F. Cochliodinium pul- 

 chellum Lebour, x720 (after K. & S.). G. Polykrikos scfnvartzi Biitschli, 

 x250 (after K. & S.). H. Pavillardia tentaculijera Kofoid and Swezy, x475 

 (after K. & S.). I. Noctiluca scintiUans, x60 approx. (after K. & S.). Key: 

 /, longitudinal flagellum; p. oral pouch; t, tentacle. 



Suborder 1. Prorocentrina. This group includes Exuviella Cienkowski 

 (178, 249, 252), Porella Schiller (252) and Prorocentrum Ehrenberg 

 (249, 252). Exuviella perforata (Fig. 4. 19, D, E) is a small marine flagel- 

 late with a thick bivalved theca. Each somewhat flattened valve is ap- 

 proximately circular in outline and shows a central conical invagination. 

 The flagella, emerging anteriorly through pores in one valve, show a 

 differentiation into longitudinal and transverse types. The two chroma- 

 tophores are yellowish-brown to yellow. 



