1862.] POWRIE OLD EED SANDSTONE. 427 



From these measurements it would appear that No. 2 was about 

 one-fourth smaller than Diprotodon australis, and that No. 1 took 

 a place between No. 2 and the latter, but nearer No. 2. The ques- 

 tion of the systematic value of the differences between No. 1 and 

 No. 2, on the one hand, and between both of these and Dipro- 

 todon australis, now arises. 



In No. 2, the outer surface of the premolar is ridged, and the 

 crown of the first molar is not so broad as it is long. 



In No. 1, the outer surface of the premolar presents simple con- 

 vexities, without ridges, and the first molar is distinctly broader 

 than long. 



In Diprotodon australis the form of the premolar is not known ; 

 the first molar is somewhat broader than it is long. 



I entertain no doubt that Nos. 1 and 2 are specifically distinct ; 

 and I propose for No. 2 the name Diprotodon minor. Whether 

 No. 1 is specifically distinct from Diprotodon australis, or whether 

 its difference in size is merely sexual, I cannot pretend to say, in 

 the absence of any premolar teeth of undoubted D. australis. 



From the very slight extent to which the premolar is worn while 

 the first molar is so much abraded, I suspect that the former tooth 

 must have persisted for a long while, instead of being pushed out at 

 an early period as in many Macroioodidce. In form and pattern the 

 premolar does not depart more widely than the molars themselves 

 from the type found in some Kangaroos, such as Halmaturus ; and 

 the cast of Zygomaturus in the British Museum shows that the upper 

 premolar in that animal had an essentially similar structure, though 

 it seems to have been somewhat larger in proportion to the molars. 



DESCEIPTION OF PLATE XXL 



Fig. 1. Part of the right upper maxilla of Diprotodon {australis ?) ; viewed 

 laterally. 



2. The under or oral face of the same fragment. 



3. A premolar tooth, apparently from the opposite maxilla of the same 



animal ; viewed from the inner side. 



4. Part of the left upper maxilla of Diprotodon minor ; viewed laterally. 



5. The under or oral face of the same specimen. 



6. Fourth molar, probably of the same specimen of Diprotodon minor. 



5. On the Old Red Sandstones of Fifeshike. 

 By James Powkie, Esq., F.G.S. 



Introduction. — In a paper which I communicated to the Geolo- 

 gical Society last year*, I stated my belief in the conformability of 

 all the Old Red Sandstones as exhibited in Forfarshire. In that 

 paper as originally framed, I had even questioned the correctness of 

 Sir C. Lyell's section of the Forfarshire rocks {' Manual of Geology '), 

 in so far as this shows an overlying unconformable conglomerate at 

 * Quart. Jom'n. Geol. Soc. vol. xvii. p. 534. 



