318 C. A. SUSSMILCH AND T. W. E. DAVID. 



and characteristic form in the Irwin region is Cyrtina 

 carbonaria var. Australasica Eth. fll., otherwise known as 

 Spiriferella (?) Australasica. This appears to be extremely 

 close to Spiriferella sarance of the Uralian and Artinskian 

 Series of Russia. The great abundance of Gastrioceras 

 near the top of the Irwin marine series also suggests a 

 Pre-Permian age for the Irwin Beds. Gastrioceras ranges 

 from Lower Carboniferous to the Artinskian. Spirifer 

 marcoui of the Kimberley area suggests a lower Uralian 

 age for the strata containing it. The fact must also be 

 emphasised that corals as Pachypora and Syringopora are 

 found at the Irwin River area, and Favosites in the 

 Kimberley Beds, the latter probably homotaxical with those 

 of the Irwin. These lend a distinctly Carboniferous 

 character to the beds at the Irwin, e.g. Syringopora (S. 

 parallela) occurs in the Gschelian Series (Upper Carboni- 

 ferous) of Russia. It is suggested that in this problem of 

 so large an assemblage of Carboniferous forms associated 

 with the Permian in the West Australian Permo-Oarboni- 

 ferous rocks that we have to deal at the Irwin and Gascoyne 

 River with a belated fauna, forms like Syringopora, Rhyn- 

 chonella pleurodon, Productus semireticulatus, Syringo- 

 thyris-like Spiriferse, etc., surviving over in the West 

 Australian bight of the ancient Tethys ocean from early 

 Carboniferous into late Carboniferous, or even perhaps into 

 Permian time. On the other hand in the Pacific fauna of 

 Eastern Australia these Carboniferous types of the Burindi 

 no longer survived over into the Permo-Carboniferous Seas 

 of that region. Just as in nummismatics, in studying an 

 assemblage of coins unearthed from one and the same 

 deposit (the date of which it is desired to determine), if the 

 coins show a variety of dates we naturally select the newest 

 and not the oldest as giving the correct date for the deposit, 

 so in a palaeontological problem like the present, more 

 weight is surely to be attached to dominant newer forms 



