UNIVERSITY OF C LIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 18, No. 15, pp. 397-4/0, lates 17-20, 19 figures in text June 27, 1918 



THE SIGNIFICANCE OF SKELETAL VARIA- 

 TIONS IN THE GENUS PERIDINIUM 



BY 



A. L. BAEROWS 





CONTENTS '(''' JUNJ2iSl7 "^J 



A. Introduction r^«,,...{/^^r^J..y;L.^3^' *^, 



Purpose and scope of this paper S&S' 



Acknowledgments 400 



Relationships and morphology of the dinoflagellates 400 



Systematic position of Peridiniiitn 404 



Nomenclature of the plates 405 



B. Main argument 408 



Abstract of argument 408 



Major skeletal characters of Peridinidae 408 



Type of antapical horn 409 



Displacement of the girdle 411 



Plate patterns 41 2 



Other skeletal characters 414 



Conclusions upon the importance of plate relationships 414 



Progressive plate development in genera of Peridinidae 416 



Possible method for multiplication of plates 419 



Regions of skeletal variation in Peridinium 424 



Plate patterns, a basis for subdivision of the genus, Peridinium 426 



Subdivisions of the genus, Peridinium 428 



Subgenus, Paraperidinium 428 



Subgenus, Metaperidinium 130 



Subgenus, Orthoperidinium 431 



Special considerations 43^] 



Summary of changes of plate pattern within a species 434 



Summary of skeletal relationships 435 



Regions of variation in the shell of Peridinium 437 



Variable regions 437 



Origin of the accessory plates , 439 



Origin of the principal symmetrical dorsal plate patterns 442 



Origin of the asymmetrical dorsal plate patterns 443 



Summary of discussion of dorsal patterns 443 



