BY G. I. PLAYFAIR. 



807 



Text-fig. 14. 

 Peridinium umbonalum var. centenniale , n. var. 



(x 800) . 



Centennial Park, Sydney (133) ; Lismore (327) . 



A small form, rounded and very nearly globose, the length 

 and breadth almost always equal. A shallow groove divides the cell 

 into two very unequal valves, the epivalve being quite two-thirds 

 of the total length . The latter is rounded and bowl-shaped, with 

 unequally arched sides and subapical eccentric pit as in P. cau- 

 datum v. guildfordense and P. geminum. Hypovalve very shal- 

 low, saucer-shaped, a mere lid gently arched behind, a little nar- 

 rower than the epivalve. Antapical plates equal (probably not 

 always however), obliquely disposed. In these rounded forms 

 there seem to be three kinds of antapical plates (1) angular with 

 straight sides, (2) angular with arched sides, (3) rounded; and 

 these appear to be interchangeable in the same form. 



Var. ovale, n. var. (Text-fig. 15). 



Peridinium parvum, ovale, ubique rotundatum, per fossam 

 transversam tenuem in partes duas maxime inasquales divisum. 

 Epivalva altissima, rotundata, alte craterif ormis ; lateribus asym- 

 metrice areuatis; fovea excentrica, subapicali. Hypovalva multo 

 quain epivalva minor paulluloque angustior, scutelliformis, pone 

 areuatis; fossa longitudinali modo dilatata, usque ad marginem 



