KOPOID AND SWEZY: UNARMORED DINOFLAGELLATA 97 



From the English, Scottish and Irish hikes, West and West (1909) record two 

 species, Gjimnodinium paradoxion and G. zacliariasi. 



These isolated references to the Gj'mnodinioidae in snch wideh^ separated 

 waters indicate a wide range in their distribution which more complete investi- 

 gations will undoubtedly greatly enlarge. They ai*e among the smallest of the 

 fresh-water fauna and hence easily escape observation. 



In the marine group of the uon-thecate dinoflagellates we find an equally 

 wide distribution. From the colder waters of the Arctic Pouchet (1894) found 

 Gymnodinium wilczeki, G. psendoiioctiluca, Pouclietia polyphemus, Poljjkrikos 

 scliwartzi, and Gymnodinium (^Gyrodinium) crassum. Meunier's work 

 (1910) in the Arctic w\as more exhaustive, but together with the great number 

 of other forms which he described he figures only three species belonging to 

 this group, i.e., Gyrodinium ftisus, G. lachryma, and G. grave. 



The remainder of the members of this group, with one or two exceptions 

 from tropical waters, are all found in the warm or cool temperate regions. 

 ]\Iost of these come from the Atlantic or the bays along the west coast of Europe 

 opening into it, including the Mediterranean. In a comparison of the lists of 

 species given for these waters and the species found by us in the Pacific it is 

 found that no great differences separate these two regions. Of the eighteen 

 species of Gyniuodiuiiim previously described from this region of the Atlantic, 

 seven have been found in the San Diego region; of the twenty-one species of 

 Gyrodinium. six occur at San Diego; of the ten species of Gochlodinium, five 

 are found at San Diego, and of the six species of Pouclietia, two are present 

 in tliis region. This gives a total of fifty-five species of these four genera found 

 in this region of the Old World, of which twenty have been identified by us in 

 the San Diego waters, with a total of ninety-two new species present at the same 

 place. The relative thoroughness of the exploration of these two regions and 

 seasonal limitations of collections probably accounts for the disparity in these 

 two series of numbers. 



Kofoid (1910rt) has pointed out the lai-ge proportion of the species of the 

 thecate dinoflagellates described from other regions and present in the Pacific 

 off San Diego. The relative proportions are somewhat greater than in the 

 non-thecate forms. This may be due in part to the fact that observations on 

 the thecate dinoflagellates have been carried on throughout the entire year for 

 a number of succeeding years, while ol)servations on the non-thecate forms 

 have been limited to the months of June, July, and August. It may also be 

 due to the greater knowledge generally of the thecate forms. 



In regard to the seasonal distribution of the unarmored dinoflagellates but 

 little can be said. Daily hauls have been made at La Jolla throughout the year, 

 ])ut only those of the suuuuer months have been examined immediately after 

 being taken. As the Gynmodinioidue cannot as a rule withstand the formalin 

 used as fixative, the hauls so treated are useless for purposes of identification 

 of this group, with very few exceptions. Our records, therefore, are complete 

 only for the months of July and August. 



