BY G. I. PLAYFAIR. 545 



Cf. P. 7^?/siZ/j/w Penard, 1891, Perid. du Leman, PI. iv., 

 f.1-3; P. java?iicum, 1908, Protococc. et Desm., PI. xvi., f. 

 575-578. The inter-tabular ridges are, in some cases, faintly 

 indicated in the epivalve. P. i?ironspiniu7n Lemm., and /^ 

 minimum Schilling, and P. Orrei Huitfeldt-Kaas, are variants 

 of this stage of development. 



Var. iNCONSPicuuM (Lemm.) mihi, forma. (PI. Iv., f.22). 



Forma hypovalva a tergo oblique excavata. 



Long. 20; lat. 1 6-18 jx. Nos.90, 100. 



Cf. G. S. West, Alg. Yan Yean Res., p.81, figs. H-J. 



Having now traced tlie development of P. tahulatum var. 

 (jranulosum through various representative stages of growth, 

 down to P. inconspicuum Lemm., 20 x 16 /ut I think it well to 

 finish the life-history by adding the development of the latter 

 (or a form of it) from the resting cell. In PI. Ivii., f.4a, is the 

 resting cell (lat. 16 /i.), the outcome of a zoospore ; while h 

 (lat. 16 /i) and c (20 x 12) show its development into the peri- 

 dinium-sheLpe, by indication of the transverse furrow near one 

 end. In c?(18xl8/x) the transverse furrow is distinct, with 

 the conical epivalve and excavated hypovalve seen in our 

 form of /'. inronspicuuni . These forms were obtained in a 

 single gathering from a piece of swampy ground at Auburn. 

 The cells were alive, but not yet motile. 



Genus Gymnodinium Stein. 

 Gymnodinium fuscum var. cornifax (Schilling). 



(PI. Ivii., f. 18,19). 



Cell, long 56; lat. 38; cyst long. 45-60; lat. corp 22-30 /.. 



Synonyms of the cysts are CI. cancer Playf., antea, 1907, 

 PI. ii., f.l6; also Reinschiella Siamensis and R. obesa W. & 

 G. S. West, Flora of Koh Chang, T.4, f. 52-54. Gi/m. fuscum. 

 G. cornifaa., G. uliginosum., and G. neglect um are all forms 

 of the same species. The last occurs here also. If the cyto- 

 plasm extends right up into the tips of the cyst, G. fusrum 



