Lower Tertlaries of the Moorahool Valley. 11 



poh'zoal limestone whicli, however, contains similar foramini- 

 fera freely scattered through it, though its great hulk consists 

 of polyzoa and spines and plates of echinoderms, together 

 with a few lamellibranch shells ; l-i species are recorded from 

 this locality. 



The base of the section is hidden by the drift of the 

 valley, but judging fr'om the close proximity of the gi'anite. 

 it is of no great deptl). 



The hill section is as follows : — 



Basalt ... ... ... ... 75 ft. 



Incoherent sandy material, witli cal- 

 careous concretions ... ... 50 ,, 



Yellow clay, with calcareous concretions 5 ,, 



Polyzoal limestone ... ... 25 ,, 



Orbitoides limestone ... ... 20 „ 



Total ... 175 ft. 



The change from tlie limestone to the yellow clay at this 

 point is a sharp and not a gradual one. The grey clay 

 which, as before mentioned, is so abundant in gastropoda, is 

 absent, having thinned out towards the granite on the flanks 

 111' which the deposit rests. 



The polyzoal limestone at the places marked (7) and (8) 

 ill {)]au is of a lighier tint than that of the well-known 

 vVaurn Ponds rock, being in places of a dazzling whiteness ; 

 liut fossil evidence shows the two deposits are of the same 

 age. We record 16 species from tlie filter quarries (see plan). 

 Near Madden's (see plan 6) a cliff section shows the following 

 interesting characters: — The polyzoal limestone forms the 

 base of the clitf. This rock in its upper portion is in most 

 places of a crystalline texture, and very few perfect shells 

 ;ire to be found in it, the fossils being represented principally 

 V>y casts. A similar state of things occurs on Sutherland's 

 (,'reek near Maude, though in the latter place gastropods, 

 especially cowries, are plentiful ; while in the true polyzoal 

 rock, they are extremely rare. Above the limestone comes 

 the clay bed. This for the fii'st few feet is full of polyzoa, 

 resembling those of the lower rock. The beds then pass up 

 in the usual manner into sandy calcareous clays with nodules, 

 and are capped by basalt. 



Though the line of demarcation between the polyzoal rock 

 and the grey clay is sharp, still, as has been just, mentioned. 



