DINOFLAGELLATA 



325 



With annulus and sulcus 

 Shell composed of plates; but no suture. . . Family 1 Peridiniidae (p. 326) 

 Breast plate divided by sagittal suture. Family 2 Dinophysidae (p. 328) 



Without annulus or sulcus Family 3 Phytodiniidae (p. 329) 



Fig. 132. a, b, Polykrikos kofoidi (a, colony of four individuals, X340; 

 b, a nematocyst, X1040) (Kofoid and Swezy); c, Peridinium tabulatum, 

 X460 (Schilling); d, P. divergens, X340 (Calkins); e, Ceratium hirundi- 

 nella, X540 (Stein); f. C. longipes, X100 (Wailes); g, C. tripos, X140 

 (Wailes); h, C. fusxis, X100 (Wailes); i, Heterodinium scrippsi, X570 

 (Kofoid and Adamson). 



