KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 415 



Key to the Genera of the Pouchetiidae 



1. Gijmnodinium- or Gyrodinium-like, girdle without displacemeut, sulcus witliout torsion .... 

 ... Protopsis gen. nov. 



1. Girdle displaced in a descending left spiral, sulcus with some torsion 2 



2. With neraatocysts Nematodinium gen. nov. 



2. Without neniatoeysts 3 



3. Without posteroventral prod or tentacle Pouchetia Schiitt 



3. With prod 4 



4. Epicone and hypocone subequal, no paracingular lines Proterythropsis gen. nov. 



i. Ej)icone less than hypocone, paracingular lines present Erythropsis Ilertwig 



PROTOPSIS gen. uov. 

 Text figure LL 



Diagnosis. — Pouchetiidae with the girdle and sulcns of the Gymnodinmm 

 or Gyrodinium type with simple or compound ocellus, no tentacle, no apical 

 loop of the sulcus, and no torsion of the body. Girdle does not make more than 

 one turn around the body. No paracingular lines. Posterior flagellar pore 

 not located far posteriorly. Three species, all eupelagic and marine. Type, 

 Protopsis nigra (Pouchet). 



Description 



To include as Lemmcrmann (1899) has done in the one genus Pouchetia 

 all Gjannodiuioidae with an ocellus but no tentacle is fraught with extreme 

 difficulty when an attempt is made to defiue this inclusiYe genus. Since the 

 coiu'se and differentiation of the girdle and sulcus is so largely utilized in 

 generic distinctions, it seems both logical and consistent to apply these criteria 

 within the ocellate forms. This necessitates the separation of those species 

 without torsion of the sulcus or its extension in an anterior loop, and with 

 far ])osterior location of the posterior flagellar pore, from those having these 

 striking modifications in structiu-e. 



The groui^ of simpler Pouchetiidae thus detached from the more complex 

 ones contains but two species, both previously described and imperfectly known, 

 that of Pouchet's (1887, pi. 10, figs. 2 A, B, 3, 4) Gymnodinium jwJyphemus 

 var. nigrum,, and that of Wright (1907, pi. 1, fig. 8) Pouchetia ochrea. The 

 former is the type spefnes of the germs Protopsis. To these a third new species, 

 P. neapolitana, is added. 



It is significant of the possible mode of evolution of the more complex 

 Pouchetiidae that Protopsis nigra has a compoimd ocellus with several lenses 

 and lobed melanosome, while P. ochrea lias at least a lobed melanosome and 

 P. neapolitana a finely divided one.' 



This fact taken in conjunction with the simplicity and primitive stage of 

 differentiation of sulcus and girdle in Protopsis suggests that the divided con- 

 dition of the ocellus and melanosomes may be the more primitive one since it is 



