44 



types of fossils to be met with. Indeed, I am of opinion that 

 the types as described in figures No. 10 to No. 23, may yet 

 prove to be common to all the members of this system. 



The only purpose for which I propose this nominal division 

 is for the better determination of sequence by an attempt to 

 classify the several members of the system from the data now 

 before me. 



To be able to do this properly, one should be thoroughly 

 acquainted with the rock systems which on every side flank 

 its borders. Unfortunately I have not sufficient leisure to 

 investigate this matter personally ; and with the exception of 

 the reference made by Strzelecki in his Fourth Epoch, 1 am not 

 aware of anything being done towards its identification. 



BOUND AKIES. 



Although Strzelecki inaccurately extended the variegated 

 sandstone as dipping towards the north at Launceston, in a 

 section running from " Dry's Bluff to Launceston," yet I have 

 reason to believe that he is correct in showing the sandstones 

 and fossiliferous limestone as dipping at a considerable angle 

 to the north-west on the Norfolk Plains, near to the Tiers. 



Flanking the north-west side of the Tamar basin, and to the 

 north of Norfolk Plains — at the village of Hadspen — a 

 variegated porous sandstone, with flakes of mica, dips towards 

 the south. 



On the north we have the greywacke, dipping at an angle 

 of about 30 degrees to the south-east, and upon the west the 

 basin is flanked by a series of greenstone ridges, which stair- 

 like, forms an inclined plane, having Ben Lomond for its 

 summit. It would thus appear that this tertiary deposit lies 

 in a trough or hollow, of upper and lower primary strata, and 

 conceals the point of junction between these older systems, 

 probably near to Longford, thus {See Fig. 29). 



LOWER ZONE. 



Having thus briefly sketched the principal boundaries of 

 the Tamir basin, I shall now address myself to describe the 

 peculiarities which characterise the division within, and which 

 I have arbitrarily divided into three zones, — the Upper, 

 Middle, and Lower. 



The most destinctive feature marking the lower zone is the 

 formation of lignite which is found to rest inconformably upon 

 greywacke on the West Tamar. 



A fine section is exposed at Muddy Creek on the West 

 Tamar. It is composed of a series of beds of blue and white 

 clays, occasionally interlaminated with thin bands of tenacious 

 clay containing leaves, the predominating types of which are 

 roughly sketched in Figs. 10 to 23. 



