344 University of California Publications in Zoology [Vol.22 



There was not often any difficulty in identifying the genus to which 

 a specimen belonged. Identification was usually fairly satisfactory in 

 case of the forms which appeared to he numerically important. 

 Certain errors in identification of species on account of the position 

 of the specimen in the counting cell were no doubt frequent. 



As in the case of diatoms it seems possihle to get a fair general 

 ■idea of the dinoflagellate population in a month by selecting the five 

 showing higher numerical averages for the month. In a list thus 

 selected four species appear throughout the four months. Ceratium 

 furca (Ehr.), Dinophysis homunculus Stein. Gonyaula.r polyedra 

 Stein, and Prorocentrum urticans Ehr. ; all are, in most cases, easily 

 identified. Of the two other species listed in the first five, Ceratium 

 fusus (Ehr.) appears in three months and Peridinium divergens Ehr. 

 in one. 



( 'i'1'tain forms which were originally recorded while counting have 

 been omitted from our final tables for one or more months because of 

 small numbers or questionable identification. Their numbers have, 

 however, been included in the total dinoflagellates. The names are 

 Ceratium arcticum (Ehr.). Ceratium breve (Ost. & Seh.). Ceratium 

 gallicum Kof., Ceratium macroceros (Ehr.), Ceratium pennatum 

 Kof., Ceratium penta,gonum Gour., Ceratium tripos (0. F. M.), 

 Dinophysis acuta Ehr., Dinophysis hastata Stein, Dinophysis acuta 

 Clap. & Lachm.. Gymnodinitim sp., NoetiJuea miliaris Surir., Oxytoxum 

 scolopax Stein, Phalacroma rudgei Murr. & Whitt., Phalacroma rapa 

 Stein, Peridinium grani Ostf., Peridinium pellucidum (Bergh), and 

 Pyrocystis lunula Schiitt. 



A number of species originally listed have been grouped together 

 in their genera or under a loosely applied species name for similar 

 reasons. This is especially true of some forms in Ceratium, Dino- 

 physis, Gonyaulax, and Peridinium. 



Paulsen's paper (1908) has been most useful in identifications. 



For economy of space, detailed discussion of species of dinoflagel- 

 lates is omitted from this paper. Kofoid's careful studies (Kofoid, 

 1907 a and b and 1911) have given much more knowledge of the 

 members of this group than is the case with diatoms. 



