THE YAN YEAN RESERVOIR, VICTORIA. 57 
upper rings (from 2-9) possess only a single series of spines as in the more 
typical forms of Triploceras gracile. Such a form as that figured on PI. 3. 
fiz. 8 is clearly but a variety of T. gracile, notwithstanding the absolute 
agreement of the basal half of the semicell with T. denticulatum. 
Although the three Australian forms from the Yan Yean area differ very 
considerably in the character of the verticillate warts, the apices all conform 
to one pattern, which on careful comparison is not so very different from that 
found in the type-form. No specimen was observed with three apical 
processes such as are figured by Playfair for T. denticulatum. 
Genus EUASTRUM, Ehrenb. 
16. Evasrrum TURNERI, West, in Journ. Linn. Soc. Bot. xxix. (1892) 
р. 141, t. 20. fig. 18. (“ Eu. sp. ad E. denticulatum accedens," Nordst. 
1888.) 
Forma MINOR. 
Forma minor, granulis paucioribus. 
Long. 21 р; lat. 15:5 ш; lat. isthm. 5 y. 
lah. Yan Yean Reservoir, at the weedy margins (common from Nov. 
1905 to Jan. 1906). 
Genus MICRASTERIAS, Ag. 
17. MicmasrERias Hampyn G. S. West, in Victorian Naturalist, xxii. 
(1905) p. 71, fig. 1; Journ. Bot. xliii. (1905) p. 253. 
M. submagna, paullo longior quam lata, profundissime constrieta, sinu 
valde aperto acutangulo ad extremum angustissimo semicellulæ trilobæ ; 
lobo polari magno et leviter exerto, parte inferiore angusta cum marginibus 
subparallelis et eum serie denticulorum cire. 7 intra marginem lateralem 
unumquemque, apicibus cum verrucis emarginatis binis et processibus minutis 
brevibus emarginatis duobus asymmetrice dispositis, angulis superioribus in 
processus longos denticulatos gradatim attenuatos sursum divergentes pro- 
ductis; lobis lateralibus profundissime bilobulatis, lobulis magnis elongatis 
denticulatis divergentibus et gradatim attenuatis ; apicibus lobulorum et pro- 
cessuum lobi polaris 4-dentatis ; cum serie denticulorum intra lobulos laterales 
et processus lobi polaris ; a vertice vise anguste fusiformes, in parte mediana 
subrhomboideæ, apices versus gradatim attenuate in processus denticulatos 
quadridentatos productæ, marginibus lateralibus denticulatis. 
Long. 198-235 ш; lat. 161-219 ш; lat. isthm. 16-18u; crass. 28 м. 
(Pl. 5. figs. 1-2.) 
Hab. Yan Yean Reservoir, abundant in the plankton for the greater part 
of the year. 
