BY W. N. BENSON. 557 



to a certain extent: parts of it are richer than the remainder in 

 fragments of keratophyre, and very coarse-grained agglomeratic 

 rock, part of which is very ferruginous, occurs immediately west 

 of the Gap. Associated with these is a red finely granular to 

 aphanitic tuff, that appears quite massive in hand-specimens, 

 save for the presence of a few larger fragments. The associated 

 cherts are interbedded with tuffaceous material, and the beautiful 

 instance of an intrusive tuff, which is discussed below, came from 

 this spot. See Text-fig. 5 and Plate liii., fig. 10. 



The mass of tuffs and breccias is invaded by a small intrusion 

 of dolerite in the southern end of the hill. On the northern end 

 of the hill, a spur runs towards the forking of the roads. This 

 consists very largely of banded claystones and grey quartzite like 

 that at Tintinhull. At the base of the hill, and following up 

 the Gap Road, is a series of limestone-outcrops. One of these, 

 the large mass exposed in portion 163, was the source of tho 

 fossils described by Mr. Etheridge from "Beedle's Freehold "(11). 

 The limestones north of the Gap are usually grey or white, and 

 are more or less associated with tuffaceous material (see p. 575). 

 South of the Gap, the limestone has a reddish colour, doubtless 

 connected with the presence of ferriferous keratophyres. (See 

 chemical analyses, p. 611). A small quarry was opened in these 

 to exploit the Nemingha crinoidal marble: several varieties of 

 ornamental stone were obtained, of which beautiful examples 

 may be seen in the museums of Sydney, particularly the Techno- 

 logi(;al Museum. [See the coloured illustration in(13)]. The stone 

 has not yet been put to much use commercially. This is the 

 typical occurrence of the Nemingha horizon, and the strati- 

 graphical details mentioned above are the grounds upon which 

 it is correlated with the limestone of Seven Mile Creek. For 

 some distance south of here, as will appear more particularly in 

 a later communication, the limestone is directly associated with 

 massive, brecciated, ferruginous rocks, keratof>hyres and the like, 

 and is separated from the Igneous Zone by a considerable thick- 

 ness of claystones and cherts. The close approximation of the 

 limesione and the Igneous Zone in the Gap must be due to fault- 

 ing. A small fault is visible by the limestone-quarry, marked bv 



