194 W. RB. BROWNE. 
graptolite-bearing beds in the neighbourhood of Cobargo, 
which lies about 44 miles from Cooma in a direction roughly 
10° S. of H. The slates are identical in appearance with 
those of Geygedzerick Hill and Wambrook Creek. The 
following forms were determined by Mr. Laseron:—Diplo- 
graptus foliaceus, - Climacograptus, Dicellograptus (2) 
gracilis, D. affinis. It would be interesting to trace the 
relations of these rocks to the Ordovician of Cooma and 
Berridale. The interposition of Silurian sediments to the 
east of Cooma suggests their deposition in.a trough or 
synclinorium of Ordovician rocks. 
(c) SILURIAN.—As the Ordovician lies, roughly speaking, 
to the west of Middle Flat and the Silurian to the east, 
and as, in spite of some discordances, the prevailing dip is 
towards the east, it is natural to assume that the upward 
sequence, or the sequence of deposition, for the Silurian 
beds is from west to east. That being so, the lowest 
sediments are slates, with interbedded limestone and brown 
quartzites, passing upwards into gritty sandstones, carbon- 
aceous shales and quartzitic sandstones alternating with 
bands of clay-shale. The limestone, carbonaceous shales 
and gritty sandstones are fossiliferous ; the other horizons 
are barren. ; 
The slates vary in colour, and are extremely cleavable 
and much jointed, splitting readily into small pieces. Their 
stratigraphical position is sufficiently determined by their 
association with the other fossiliferous beds. } 
The limestone runs in a general N.N.W. direction and 
forms a belt about 4 miles long. Its northern end, which 
disappears under the alluvials of Cooma Creek, has a width 
of outcrop of over 1,000 yards; this gradually decreases 
as one goes south, till at Toll Bar Bridge it is not more 
than 100 yards. The main mass disappears here, but the 
belt continues southwards as a series of small isolated 
