810 PERIDINEAE OF NEW SOUTH WALES, 



A neater, less strongly faceted, more regular form, with the 

 plates only slightly concave. The epivalve is broadly conical, 

 in optical section triangular; sides almost flat; apical pit present 

 but less pronounced, rim not produced. Hypovalve somewhat 

 depressed, subtruncate furnished with three small spines behind. 



Peridinium striolatum, n.sp. (PL xli., f. 1) . 



Peridinium magnum, ovale vel ovatum, fossa transversa cireu- 

 lata (vel minime spirali) in partes duas inasquales divisum; a 

 vertice visum multo compressum; membrana per longitudinem 

 crasse striata. Epivalva rotundato-conica, baud angulata, ad 

 apicem late-rotundata ; tabulis axmatoriis 7; apicalibus dorsalibus 

 4 (medianis hexagonis 2, lateralibus pentagonis 2) ; tabulis apica- 

 libus ventralibus pentagonis 2; tabula rhomboidea plerurnque ro- 

 tundata, circulata vel ovali; fossa longitudinali (parte superiore 

 in epivalva) plerumque longissima et cum tabula rhomboidea plus 

 minus coalita. Hypovalva crateriformis, interdum plus minus 

 angulata; fossa longitudinali pone dilatata usque ad marginem 

 posteriorem extensa; tabulis antapicalibus sequalibus, depressis, 

 ad latera protractis, sagpe oblique dispositis. 



Long. 44-48, lat. 34-38, epiv. alt. 23-25, crass. 23 ^ 



Centennial Park, Sydney (133) ; Botany (17) . 



This large handsome species is characterised by its membrane 

 regularly longitudinally coarsely striate. In general shape it is 

 oval, in end view compressed. The epivalve which measures 

 nearly half the length of the cell, is bell-shaped or conical, 

 broadly rounded above, not faceted. The hypovalve is bowl- 

 shaped, generally faceted, equal in breadth to the epivalve. The 

 longitudinal furrow is dilated behind and extends right back to 

 the posterior margin of the cell. There is a tendency for this 

 dilated portion to be shut off from the rest, the furrow being 

 constricted and an imperfect ridge often formed. The length of 

 the longitudinal furrow within the epivalve is remarkable and 

 characteristic of the species in all its forms as is also the shape 

 of the rhomboidal plate. The latter is almost always rounded, 

 circular, ovate or oval, extending nearly to the apical margin of 

 the valve, and seems in many cases to be merely a dilatation of 

 the furrow. The antapical plates also have well-marked charac- 

 ters, being depressed and spread out laterally. 



Var. rugosum, n. var. (PL xli., f. 2) . 



Forma hypovalva magis angulata, tabulis concavis; tabulis an- 



