244 



QUEENSLAND SPECIES OF ARCELLA, 



Island, CheJiner, Graceville, Beerl)urrum, and Maryborough).* 

 Fuithermoie, material gatheied during the minimum period 

 Sept.- Dec, sliows a different dominant form (see Cooroy and 

 West Burleigh). A feature of considerable importance in this 

 connection is, that the most southerly and .the most northerly 

 locality are ai)Out 190 miles apart, viz., West Burleigh and 

 Maryboi'ough 



Fig.2, A. discoides. Tlie values in this graph are mostly small, 

 a!id, out of eighteen observations, eleven range from 5% (6th 

 Oct., 30th Oct., 28th Dec, 1916; 30th Jan., 28th Feb., 29th 

 March, 2nd May, 31st May, 28th June, 31st Aug., 12th Sept.. 

 1917). There is only one prominent maximum (86%, 2Sth Nov., 

 1916). 



Until more data arc (collected in the case of this species, aiid 

 of A. mitnUa. it is considered premature to draw conclusions, 

 though there is reason to believe November is a maximuni 2)eriod. 



SO 



^0 



30 



to. 



10. 





Oct. Nov. Dec. Ja/n. Feb. Ma-r. Apl. Miy Jan. Jul. Auj. Sep. Oct. Nov. Dec. 



Fi^'.o. — Percentage-frequency (if A. mitrnta in Arcellan fauna. IJrisbanc 

 IJotanical (Jardens : Sept. -illth. lUlC, to Dec. 29th, 1917. 



Fig. 3, A. mitrafa. Three maxima are present (30th Oct., 191G: 

 28th June, 2nd Nov., 1917) and of these, two (30th Oct., 1916, 

 and 2nd Nov., 1917) occur during the maximum period of J. 

 vulgaris. On only one occasion did the percentage fall belo^^ 

 0% (1% 31st Aug., 1917). It is the most consistent form of the 



* '24tli Nov. is sntticientlj' near December to V)c included in the maxiunuii 

 period. 



