SURVEY OF THE ORDER PERIDINIALES 



G. At least three antapical plates present 



Pyrophacaceae 



H. On ventral side of epitheca where intercalary striae 

 converge, there is a small but conspicuous field 

 with a porelike point Heterodlniaceae 



H. Epitheca on the ventral side without such porelike 

 point I 



I. Cell with two to four characteristic horns; one 



apical, one to three antapical . . . Ceratiaceae 

 I. Cell not so shaped J 



J. Theca so strongly reticulated on the surface that the 

 tabulation is not discernible . . Protoceratiaceae 

 ]. Tabulation clearly evident K 



K. Posterior intercalary present in addition to one ant- 

 apical Gonyaulacaceae 



K. Two antapicals present Peridiniaceae 



K. Three antapicals present, one dorsal, two ventral . 

 Goniodomaceae 



K. Only one plate at the antapex; not drawn out . . L 



L. Shape spherical, without apex . . Dinosphaeraceae 

 L. Cell flattened; apex present; comb near sulcus . . 

 Diplopsalis 



Genera 



The genera of the Peridlniales are described prin- 

 cipally on the basis of the number and arrangement of 

 the thecal plates. For purposes of terminology these 

 plates can be arranged more or less in rows running 

 parallel to the girdle. In this report the terminology of 

 Kofoid (1909) has been followed. On the epitheca, ante- 

 rior to and touching the girdle, is a row of plates, the 

 precingular series. Another group of plates, touching 

 . the apex, is designated the apical series. Between 

 these two rows there may be interpolated plates called 

 the anterior intercalaries. The girdle itself is made up 

 of a series of plates. On the hypotheca there is a row 

 bordering the girdle called the postcingular series. 

 Another series, touching the antapex, is called the ant- 

 apical plates. Between these and the postcingular ser- 

 ies there may be interpolated other plates which are 

 designated the posterior intercalaries. In the plate for- 

 mulas the names of these plates have been abbreviated 

 in the present paper as follows: 



apical platelet - pi postcingular - po 



apical plate - ap posterior intercalary - p 



anterior intercalary - a antapical - ant 



precingular - pr sulcal - s 

 girdle - g 



These abbreviations are clearer and more rapidly read 

 than the prime signs used by Kofoid (1909). 



The following list of genera of the Peridlniales is 

 compiled chiefly from Lindemann (1928). There is con- 

 siderable uncertainty in regard to the limits of some 

 genera. For example, the genus Diplopsalis includes 

 five genera considered distinct by some authors. The 

 plate formula is given as far as is known for each genus. 



Acanthogonyaulax (Kofoid) nobis. Sap, Oa, 9pr, 6g, 7s, 



6po, lant. 

 Amphidoma Stein, 1883. 6ap, Oa, 6pr, 6g, ?s, 6po, Ip, lant. 

 Blepharocysta Ehrbg., 1873. 2ap, l-2a, 6pr, ?g, ?s, 



3po, 3ant. 

 Centrodinium Kofoid, 1907. 2ap? Oa, 6pr, ?g, ?s, 5po, 



Ip, 4ant. 

 CeraUumSchrank, 1793. 4ap, Oa, 5pr, 4g, ?s, 5po, Op, 2ant. 

 Ceratocorys Stein, 1883. 2ap, 2a, 5pr, 6g, 5-6s, 5-6po, 



Cladopyxis Stein, 1883. 4ap, Oa, 8pr, ?g, ?s, 6po, Op, 



2ant. 

 Congruentidium Ab^, 1927. 4ap, la, 5pr, ?g, ?s, 5po, 



Ip, 2ant. 

 Dinosphaera Kofoid and Mich., 1912. 3ap, la, 6pr, 6g, 



?s, 5po, Op, lant. 

 Diplopsalis Bergh, 1882. 3-4ap, 0-2a, 6-7pr, ?g, ?s, 



5po, Op, l-2ant. 

 Dolichodinium Kofoid and Adamson, 1933. 4ap, Oa, 6pr, 



6g?, ?s, 6po, Op, 3ant. 

 Glenodinium Stein, 1883. Variable pattern. 

 Glenodiniopsis Wolosz., 1916. 7ap?, Oa?, 8pr, ?g, ?s, 



7po, 2ant. 

 GonyaulaxDiesing, 1886. Formula for genus uncertain. 

 Goniodinium PaviUard, 1927c. 4ap, Oa, 6pr, 9g?, ?s, 



6po, 2a, 3 ant. 

 Goniodoma Stein, 1883. Sap, Oa, 7pr, 6g, 5s, 5po, Op, 3ant. 

 Heterocapsa Stein, 1883. 4ap, 2a, 6pr, ?g, ?s, 5po, Op, 



2ant. 

 Heterodinium Kofoid, 1906. Sap, la, 6pr, 6 (7?) g, ?s, 



7po, Op, 3ant. 

 Lissodinium Matzenauer, 1933. S(2?)ap, Oa, 5pr, ?g, 



?s, 5po, 4ant. 

 Murrayella Kofoid, 1907. 2-4ap, la, 6pr, ?g, ?s, 4po, 



Op, lant. 

 Ostreopsis J. Schmidt, 1901. Sap, Oa, 7-8pr, ?g, ?s, 



4po?, lant? 

 Oxytoxum Stein, 18 8S. Sap, Oa, 5pr, ?g, ?s, 5po, Op, lant. 

 Pachydinium Pavillard, 1915. 3ap, Oa, 5pr, ?g, ?s, 5po, 



Op, Sant. 

 Peridiniella Kofoid and Mich., 1911. 4ap, Sa, 7pr, 6g, 



?s, 6po, Ip, lant. 

 Peridinium Ehrbg., 1840. 2-5ap, 0-8a, 6-7pr, 3-6g, 5- 



6s, 5-6po, Op, 2ant. 

 Podolampas Stein, 1883. 2ap, la, 6pr, ?g, ?s, Spo, 4ant. 

 Protoceratium Bergh, 1882. 2ap, Oa, 6?pr, 6?g, ?s, 



6po, Op, Sant. 

 Pyrodinium Plate, 1906. 3ap, Oa, 6-7pr, 8g, ?s, 5po, 



Ip, lant. 

 Pyrophacus Stein, 1883. 5-9ap, 2?a,9-13pr, ?g, ?s, 9-13 



po, 0-2p, 3-4ant. 

 Spiraulax Kofoid, 1911. 4ap, la, 6pr, 6g, 6s, 6po, Ip, 



lant. 



State of Knowledge of Morphology 



In the above list there are thirty genera covering 

 more than five hundred species. Although the generic 

 classification of these species is based primarily on the 

 plate pattern, our knowledge of this feature is far from 

 complete, as can be seen by a glance at the above list. 

 Many generic diagnoses are based on the analysis of 

 only one or a few species. In many cases the tabulation 

 given by the authors is admittedly only approximate. 

 Some of the recorded generic plate formulas are decid- 

 edly incomplete; e.g., for five genera not even the major 

 plates of the epitheca and hypotheca have been reported 

 with certainty. Among those genera for which formulas 

 of the major epithecal and hypothecal plates have been 

 reported without reservation, seventeen have not had the 

 number of girdle plates reported or this number is un- 

 certain. In only three genera had the ventral area been 

 investigated before the present work. 



Under these conditions it is a matter of course that 

 all the generic diagnoses may be subjected to more or 

 less radical alterations on the application of more crit- 

 ical morphological analysis. Further, a more extensive 

 study of the various species will undoubtedly result in 

 revised concepts of genera as weU as of species. 



Over 1200 papers have been written on the Peridin- 

 eae. More than 900 of these contain systematic or flo- 



