A Ncic Speciefi of Geratodus. 27 



which it seems to ilift'ev only in the less iiuuiber of denticles. Re- 

 garding this latter featuie. Smith Woodward remarks,! in speaking; 

 of the Jurassic form C ants, which likewise has only four den- 

 ticles, " The multiplication of the denticles has already been^ 

 observed in the teeth of certain sharks as they are traced onwards 

 in time; the same phenomenon obviously occurs in C'erafodvs/' 



Conclusions. 



The occurrence of a tooth of C'rrafodus in the Upper Cretaceoii'- 

 New Sf)uth Wales helps to link up the fossil Australian species with 

 the living Ceratodus (Neoceratodus) of Queensland. The older 

 form. C. anus, like the present, in shoAving only four denticles as 

 against six in the living species, bears a close affinity to the Creta- 

 ceous species, C. wollastoni. On the other hand, the surface of" 

 attrition in the Cretaceous tooth has a .structure almost identical 

 with the tooth of the living lung-fish, distinguishing it in this 

 respect from the comparatively coarsely reticulated surface seen in 

 the Jurassic species, Ceratodus avus. 



In consideration of the fact that a fossil scale of Ceratodus iden- 

 tical in l)oth form and structure with the living lung fish- has been; 

 found in the same series of Jurassic strata in Gippsland^ wdiich 

 contained the tooth of Ceratodus arus, the evidence for associating 

 the Juiassic specimen (and at the same time the present Cretaceous 

 form) with both genus and subgenus of the living mudfish, were it 

 not for the number of denticles on the tooth, Avould seem to be 

 almost conclusive. In view of the intermediate oi- annectant charac- 

 ters of the Jurassic and Cretaceous with the living species of Aus- 

 tralia, the subgeneric name of Metacerafodus is here suggested. 



EXPLANATION OF PLATES. 



Fig. ]. — Ceratodus (Metacerafodus) wollastoiit , subgen. et sp. 

 nov. Kight mandibular tooth. Upper Cretaceous, W^algett, New 

 South Wales. Nat. size. 



Fig. 2. — Ditto. Outer aspect of tootii. Nat. size. 



Fig ."'>. — Ditto. Denticle enlarged, to show the nature of the 

 pitted outei- surface, x 2. 



1 Lof. supra cit., 1006, p. 2. 



•2 The native name " Barramunda" jfiven to the liiii{f-fi.sh is applied to any larjfe river fish inr 

 Queensland, and according,' to some authorities (see D. G. Stead, "Fishes' of Australia," 190<i, p. 

 229), properly belonj^s to the osteojjlossid, Scltrupagen leichardti. The native name " djelleh " es- 

 pecially denotes the lung-fish. 



3 Rec. Geol. Surv. Victoria, vol. iii., pt. 2, 1912, p. 234, pi. xxxix. 





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