Yol. 62.] TARANXOX SERIES OP TARANXON. 650 



rather than of grits, may be inferred from the more gentle fall of the 

 river-bed and from the absence of good rock-exposures. Xo search 

 for graptolites was made in these shaly bands, but doubtless they 

 are to be found at certain horizons. 



This softer shale-band is underlain by more gritty strata, 

 constituting a thin but well-marked grit-band (4th) of some 35 feet, 

 and forming the top of the largest waterfall in the upper course of 

 the Tarannon River. 



Beneath this comes the 4th shale-band, which forms the floor of 

 the waterfall, and is of about the same thickness. It contains a 

 few darker gre}~ or black shale -layers, from which the following 

 graptolites were identified : — 



Monograptus priodon (C). Monograptus subeonicus (C). 



Monograptus griestonensis (C). Monograptus Marri, Perner (C). 



Monograptus discus (C). Monograptus nudus (C). 



The bottom of the waterfall is constituted by the 3rd grit-band, 

 which is similar in thickness and character to the one overlying it. 

 At the foot of this waterfall the Trwstnant stream joins the main 

 river on its right bank. This stream, in the lower part of its course, 

 has cut a deep and narrow gorge along the strike of the beds belonging 

 to the 3rd grit-band. A good fossiliferous locality was detected in 

 the northern bank about 2 feet above the topmost grit-bed, and from 

 a thin shale-layer all the graptolites mentioned above were collected. 



For a distance of about 60 yards below the waterfall the beds 

 are only exposed incompletely in the left bank. The 3rd grit-band, 

 however, is seen to be underlain by a more shaly group (3rd shale- 

 band), while below this again the occurrence of occasional grits from 

 1 to 2 feet thick clearly indicates the presence of a 2nd grit-band, 

 though its extent and detailed character are here indefinite. 



The 2nd shale-band intervenes between this and a first and lowest 

 grit-band, which is well shown at the point where the river makes 

 a sharp bend to the north-east, almost at right angles to its previous 

 course. This 1st grit-band contains several grits of 1 and 2 feet in 

 thickness, but there is, on the whole, a greater proportion of shales 

 than in the overlying grit-bands. Two normal faults cut the strata 

 at this point and throw the beds down to the west, but do not 

 displace them more than 10 and 20 feet respectively. It is possible 

 that similar faults may affect the beds belonging to the 2nd shale- 

 band above ; but they have not been detected, owing to the fact that 

 the rocks are to a great extent obscured by vegetation. 



The lowest important assemblage of grits is underlain by the 1st 

 shale-band, which is of considerable thickness and contains six grits 

 of about 8 to 14 inches near its centre. Some 40 feet below these 

 grits, at a point where the river makes another sharp bend to the 

 east, a thin dark shale-layer and an overlying bed of greywacke' 

 yield most of the species of graptolites which have yet been detected 

 in the upper beds of the Talerddig Group, namely : — 



Monograptus priodon (C). 

 Monograptus griestonensis (f. C). 

 Monograptus Marri (C). 



Monograptus nudus (C). 

 Monograptus suhconicus (f. C). 

 Monograptus discus (f. C). 



