544 PLANKTON OF THE SYDNEY WATER-SUPPLY, 



transverse ordinatis instructis. Partibus apicalibiis antapicali- 

 busque rugis ornatis. 



Long. 54; lat. 54 [i. Cum priori. 



Var. OVATUM, n.var. (Pl.lv., f.l4). 



Forma ovata; fossa transversa centrali; membrana glabra; epi- 

 valva conica; hypovalva rotundo-conica; tabulis a rugis minute- 

 granulatis definitis. 



Long. 50; lat. 46 /a. Filter-sample 115. 



Cf. Penard, Perid. du Leman, PI. iii.,f.9, for a similar ridging. 



Var. INTERMEDIUM, n.var. (PI. Iv , figs. 15, 16). 



Formae inter var. africanum et var. granulosum intermediae, 

 ovales; fossa longitudinali valde dilatata; tabulis plus minus 

 inchoatis; membrana glabra. 



Long. 42-44; lat. 29-40 />i Filter-samples 100, 102. 



Var. APRicANUM(Lemm.) mihi, foi-ma. (PI. Iv., f.l7). 



Long. 30-32; lat. 27-28 /x Filter-sample 66. 



Cf G. S. West, Third Tanganyika Exp., PI. 9, f.l. This is a 

 young stage of growth intermediate in position between var. 

 intermedium above, and var. pttsilhim{ Penard). Its likeness, in 

 shape, to the latter, in our specimens, is very decided, especially 

 in the excavation at the back of the hypovalve, which marks the 

 position of the greatly dilated longitudinal furrow. Also in the 

 rectangular produced apex of the epivalve, which sometimes 

 shows the two minute teeth of var. granulosum, the full-grown 

 form 



Var. CAUDATUM, n.var. (PI. Iv., f.l 8). 



Forma ovata, var. africano proxima; membrana glabra; tabulis 

 non perfecte definitis. Epivalva apice producta; hypovalva a 

 tergo dentibus binis instructa. 



Long. 30; lat. 21 /x. Filter-sample 66. 



Var. PusiLLUM (Penard) mihi, forma morsa, n.f. 



(PL lv.,f. 19-21). 

 Forma hypovalva a tergo oblique excavata. 

 Long. 20-24; lat. 16-18 /t. No 66. 



