Brachiopoda. <[ 



160 THE GEOLOGY OF THE CANOBOLAS MOUNTAINS, 



Spoxgida. Astylospongia. 



\ Bronteus sp.ind. 

 Tkilobita. \ o/ • 1 



I Phacops sp.ind. 



Conchidium (^Pentainerus) Knightii var. stricta. 



,, ,, Etheridgii. 



Anoplotheca{]) australis. 



Cainarotoe,chia{V) Silssmilchii. 



Conocardium Davidis. 



Orthisina{1) . 



Cjiinoidea. Crinoid stems. 



Carhoniferous(i). — Extensive intrusions of augite-porphyrite 

 (diabase-porphyry) occur, intruding the Silurian slates in the 

 northern part of the area. These are well exposed along the 

 Forbes Road, and in the cuttings of the Forbes-Molong Railway 

 line. These intrusions possibly took place during the Carbon- 

 iferous Period. 



Tertiary. — (a) Volcanic. These are classified as follows : — 



{a) Leucocratic Trachytes including Comendites, Pantellarites, 

 light-colourrd Arfvedsonite-Trachyte^^, etc., with their correspond- 

 ing dyke-rocks. They are all typically light-coloured, and more 

 or less acidic in composition, 



(6) Melanocratic Trachytes, including Phonolitic Trachytes, 

 Trachy-Andesites, with their corresponding dyke-rocks and tuffs. 

 These are typically darker in colour than the previous group, and 

 some of them might easily be mistaken for andesites in the hand- 

 specimens. 



(c) Andesites, mostly porphyritic, and inclined to basic in 

 composition. 



(il) Olivine-Basalts. 



(b) Diatomaceous Earth.— One deposit was observed in the 

 Parish of Bowan, near the Cargo Road. The mode of occurrence 

 was somewhat obscure, but it appeared to lie below, and there- 

 fore to be older than the Andesites. 



The Diatoms belong largely to the genus Melosira, while 

 sponge-spicules {Spongilla) are also abundant. 



