THE ARMOURED DINOFLAGELLATA : II. PROROCENTRIDAE AND DINOPHYSIDAE (A)

Abstract

Many elaborate or voluminous monographic works of armoured dinoflagellates have been presented, leaving, however, some or other important taxonomical problems almost or entirely unsolved. It may be fruitless to carry on taxonomical studies on any groups of dinoflagellates, putting undue stress upon structural features, morphologically distinct but taxonomically insignificant. Within several years after the present author commenced his morphological study of this group of dinoflagellates, he gradually learned that almost every former investigator had failed in estimating all of the available morphological features for the purpose to find in them some significance taxonomically very important. This was mentioned, though very briefly, in one (1936) of his previous papers in regrad to the genus Peridinium. GRAHAM (1942), paying due consideration to this, stated that "The ventral area was almost unknown in the Peridiniales when this investigation was started. Since then, however, ABI?. (1936) has begun a reclassification of the genus Peridinium on the bases of the structures of this regions, and T AI and SKOGSBERG ( 1934) have demonstrated the importance of this feature in the Dinophysiales." In regard to Dinophysidea, which corresponds to KoFOID and SKOGSBERG's (1928) Dinophysoidae, the present author found a structural feature which is in the closest connection with the ventral area and regarded as of the most taxonomical importance, although T AI and SKOGSBERG had overlooked it. This paper was written, focussing his considerations on his own observations on one hand and on the review of all available literature on the other hand, in hopes of further advancement of the studies of this animal group.