274 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 24, 



What lapse of time is represented during this period of erosion is 

 a matter of speculation ; but it seems certain tliat the Mollusca of the 

 present creeks Avere also the inliabitants of the waters during the 

 whole period of denudation since the last volcanic eruption. 



From the Gulf of Carpentaria in the north to Darling Downs in 

 the south, however, the fossil remains of extinct mammalia have been 

 found in breccias and indurated muds, which are representatives of 

 the beds of old water-courses through which the present creeks cut 

 their channels. At Maryvale Creek, in latitude 19° 30', south, good 

 sections of these old brecciated alluvia occur, a view of one of which 

 is here given (Fig. 2). The fossils from this section, as determined 



Fig. 2. — Vieiu o/ Diprotodon-Jreccms, Maryvale Creeic, Northern 

 Queensland. Lat. 19° 30' S. 



''^-^^k-' 



by Professor Owen, are Diprotodon austndis, Alacropus titan, Thy- 

 lacoleo, Phascolomi/s, Nototherium, Crocodile teeth, &c. 



Imbedded in the same matrix occur several genera of mollusca of 

 species undistinguishable from those inhabiting the Maryvale Creek. 

 My friend and late colleague, Mr. liobert Etheridge, jun., has com- 

 pared these with the recent forms, and finds them to consist of: — 



Gasteropoda. 



Melania pagoda. 

 ,, area. 

 ,, subimbricata. 

 „ mcesta. 



Melania, sp. 

 Limna?a rimosa. 

 Physa truncata. 

 „ sp. 



Corbicula ausfcralis. 



Lamellibranciiiata. 



I Unio, sp. 



The fact of these older alluvia forming both the bed and banks of 

 the present water- course (as seen also in the section delineated). 



