144 The Mastigophora 



tion of the sulcus is expanded into a deep pouch extending to the base 

 of the tentacle. 



Suborder 3. Peridinina. A theca composed of separate plates is charac- 

 teristic. Such features as relative size of the epicone and hypocone, extent 

 and torsion of the girdle and sulcus, and the number and arrangement 

 of thecal plates are important in taxonomy. Three small families differ 

 from the rest with respect to development of the girdle. In the Sino- 

 diniidae, the girdle is an irregular belt, instead of a groove, and shows 



Fig. 4. 21. A-D. Glenodinium cinctum Ehrbg., x580 approx. (after Eddy); 

 ventral, apical, dorsal, and antapical views. E. Hemidinium nasiitum Stein, 

 ventral view showing girdle, sulcus, and thecal plates; schematic (after Wolo- 

 szynska). F. Palmella stage of H. nasutum; schematic (after Baumeister). G-J. 

 Diplopsalis lenticulata Bergh; x700 (after Lebour); ventral, lateral, antapi- 

 cal, and apical views. K, L. Heterodinium scrippsi Kofoid, dorsal and ventral 

 views; plates numbered; x350 (after K.). 



