806 PERIDINEAE OF NEW SOUTH WALES, 



tenui . Epivalva latissirue eonica, subtriangularis ; fovea apicali ; 

 lateribus symmetricis fere rectis; tabulis aequatoriis altissiniis. 

 Hypovalva valde excavata pa?ne truneata, interdum spinis rninu- 

 tissimis binis armata, lateribus rectis, fossa longitudinali latis- 

 sime dilatata; tabulis antapicalibus maxime inaequalibus . 



Long. 19-25, lat. 19-22 ^ Botanic Gardens, Sydney (3) . 



A very distinct form, but the plates in dorsal and ventral view 

 are as in the type. The cell is very angular, the length and 

 breadth nearly eflual. The epivalve is very broadly conical and 

 so flat in the sides as to be almost exactly triangular in optical 

 section. The equatorial plates again very deep. The hypo- 

 valve is so deeply excavated as to be almost truncated and the 

 widely dilated longitudinal furrow is merged in this excavation. 

 The sides of the hypovalve are flat and the posterior angles often 

 tipped with a minute spine. The antapical plates are very un- 

 equal, one large and almost square, the other very narrow, differ- 

 ing in this both from the type and from var. elegans. I have 

 this form only from a tank in the Botanic Gardens, Sydney, fed 

 by the city water. 



Peridinium umbonatum var. inaequale Leinin. (Text-fig. 13). 



Forma fossa transversa fere mediana, hypovalva major, vix 

 angulata, tarn lata quam epivalva ; in epivalva fovea apicali nulla. 



Long. 22i, lat. 19, epiv. alt. 10£, lat. f oss. trans. 3 p.. Bris- 

 bane. 



A single cell noted in a plankton sample from Brisbane. It 

 does not quite agree with Lemmermann's figure given by Schil- 

 ling, I.e., p. 40, f. 44. The transverse furrow is nearly median, 

 the hypovalve therefore deeper. The latter is as broad as the 

 epivalve and hardly faceted at all . There is no apical pit, a very 

 unusual thing in all forms of small species in our waters. I did 

 not manage to secure end views. 



Var. cextenniale, n.var. (Text-fig. 14) . 



Peridinium parvum, subglobosum, ubique, rotundatum, hand 

 angulatum, fossa transversa in partes duas maxime inasquales 

 divisum; fossa transversa tenui, in spira disposita. Epivalva 

 rotundata, crateriformis, fovea subapicali instructa, lateribus 

 asymmetricis . Hypovalva tenuissima, scutelliformis, pone con- 

 vexa, multo quam epivalva minor et paullulo angustior; fossa 

 longitudinali modo dilatata usque ad marginem posteriorem ex- 

 tensa; tabulis antapicalibus aequalibus, modo oblique dispositis. 



Long.=lat.=30-44, crass, c. 32 /x. 



