BY G. I. PLAYFAIR. 



805 



shallow, the longitudinal furrow short, and distinctly outlined. 

 Apart from the pointed conical almost triangular epi valve, the 

 chief characteristics are the depth of the equatorial plates in 

 proportion to the height of the epivalve, and the rhomboidal 

 plate, which is arched above, its outline often resembling a loop. 

 The antapical plates are quite regular. 



Var. excavatum, n.var. (Text-fig. 11). 



Forma ovata vix angulata. Epivalva conica, fovea apicali, 

 lateribus symmetricis quam levissime areuatis; tabulis aequatoriis 

 altissimis, tabula rhomboidea longissima. Hypovalva pone 

 oblique excavata, interdum spinis minutis binis armata; fossa 

 longitudinali valde dilatata usque ad marginem posteriorem ex- 

 tensa . 



Long. 16-21, lat. 14-154 p. Sydney Water Supply (64, 66) . 



A minute form, in shape like var. elegans, but with the hypo- 

 valve considerably excavated behind, where it is sometimes armed 

 with a couple of minute spines. The longitudinal furrow is 

 greatly dilated and extends right back to the hinder margin of 

 the hypovalve. This form also has very deep equatorial plates 

 in the epivalve. The markings were extremely faint, and I was 

 not able to make out the end view at all. 



Var. angulosum, n.var. (Text-fig. 12). 



Forma angulosa, prae longitudinem latissima, fossa transversa 



Text-fig. 12. 



Peridinium geminum 



var. angulosum, n. var. 

 (a) dorsal view, (b) ventral 

 view, (c) hypovalve (x 1000). 



Text-fig. 13. 



Peridinium umbonatum 

 var. inaequale, Lemm., 



forma, (x 1000) 



