KOPOID AND SWEZY: UNARMORED DINOPLAGELLATA 131 



Subgenera of Amphidinium 



Subgenus 1. Amphidinium subgen. no v. 



Bod}^ compressed either dorsoveutrally or laterally. Type species A. oper- 

 cidatiim Claparede and Lachmann. This subgenus includes besides the type, 

 A. corpnlentum sp. nov., A. dentafiim sp. nov., A. herdmani nom. sp nov., A. 

 klehsi nom. sp. nov., A. ovoideum. Lemm., A. scissum sp. nov., A. steini (Stein), 

 A. sulcatum. Kofoid, and A. trim cat urn sp. nov. 



Subgenus 2. Rotundinium subgen. nov. 



Body not compressed, its dorsoventral and transdiameters being subequal. 

 Type species A. cucurMta sp. nov. This subgenus contains in addition to the 

 type the following species: A. asi/mmetricmn sp. nov., ^1. cucurhiteUa sp. nov., 

 A. fastigium sp. nov., A. galhanum sp. nov., A. lacustre Stein, A. pacificum 

 sp. nov., A. turho sp. nov., A. vasculum sp. nov., and tentatively the following 

 imperfectly described species, A. crassimi Lolunann, A. longum Lohmann, and 

 A. rotundatum Lohmann. 



Key to the Species of Amphidinium 



1. Body compressed either dorsoventrally or laterally (subgenus Amphidinium) 2 



1. Body circular in cross-section or nearly so (subgenus Rotundinium) 11 



2. Epicone small, less than 0.5 transdiameter in diameter, body compressed dorsoventrally 3 



2. Epicone greater than 0.5 transdiameter in diameter 6 



3. Surface without striae 4 



3. Surface striate klebsi nom. sp. nov. 



4. Chromatophores minute, rounded, numerous ovoideum Lemm. 



4. Chromatophores large 5 



5. Chromatophores long, radial operculatium Clap, and Lach. 



5. Chromatophores irregular steini (Stein) Lemm. 



6. Body compressed laterally sulcatum Kofoid 



6. Body compressed dorsoventrally '' 



7. Sulcus extending anteriorly to apex 8 



7. Sulcus extending only to the girdle 9 



8. Chromatophores absent, surface striate scissum sp. nov. 



8. Chromatophores present, no surface striae corpulentum sp. nov. 



9. Hypocone striate, minute green chromatophores truncatum sp. nov. 



9. Hypocone not striate, chromatophores larger 10 



10. Chromatophores green, disk-shaped dentatum sp. nov. 



10. Chromatophores yellow, long, radiating from center herdmani nom. sp. nov. 



11. Large species, over 75/n in length 12 



11. Small species, not over 75/i in length 16 



