SILURIAN AND DEVONIAN ROCKS. 135 
IV. DEVONIAN. 
The following Devonian strata occur (in descending order) 
1 Quartzites and sandstones ... .. oo2teet thick 
2 Shale and sandstone (Lingula Beds) 
with Lingula, Spirifer, Rhynconella etc. 186 a 
3 Massive red sandstones ae wae 200 ee 
4 Red and green shales... uae ww. 304 i 
5 Conglomerates with interbedded red 
shales and sandstones 500 vee 412 a 
Total thickness ... ... 1484 feet 
This represents only a portion of the original thickness 
of the Devonian formation, since much has been removed 
by denudation. Where Oaky Creek has cut its valley 
across these beds, only the lower 300 feet still remain. 
The Basal Conglomerates.—These, with their associated 
bed of red shales and sandstones form the basal beds of the 
series. The conglomerates consist of waterworn pebbles 
of limestone, indurated shales, cherts, quartz, etc.; these 
range in size up to 4 inches in diameter, but the majority 
do not exceed 13 inches. The cementing material consists 
of sand, clay, and ferric oxide. Some of the limestone 
pebbles contain recognisable fossil corals (Favosites and 
Heliolites), and were evidently derived from the Silurian 
limestones. 
The Red and Green Shales.—These are thinly bedded 
and not fossiliferous; they display no features of special 
interest. 
The Massive Red Sandstones.—These are coarse-grained, 
passing in places into conglomerate. The cementing 
material is largely ferric oxide, giving these strata a 
typical ‘‘old red sandstone”’ appearance. They frequently 
exhibit false-bedding, but contain no fossils. 
The Lingula Beds.—These are a series of thinly-bedded 
shales and sandstones (Plate 14), containing abundant evid- 
