part 3] SUCCESSION or the ayonian at clifton. 227 



Liflwstrolloii martini, meets the floor o£ the quany just behind 

 the wall of the miniature range. Some 3 feet lower down is 

 another Litliostrotion band, and this, with the exception of the 

 Diphi/pliijllum band already described, is the lowest level at which 

 Lithostrotiont corals are found in the section. China-stones are 

 again met with at the level of the ' back slope,' where a band 

 crowded with Seminulce is conspicuous. Many of them show the 

 spiral arms, and others enclose patches of calcite due to the 

 recrystallization of calcareous mud, A big fallen block of lime- 

 stone at the northern end of the Great Quarry has the bedding- 

 plane (PI. VIII, fig. 3) covered with elongated bodies, presumably 

 concretionary in character and resembling those described and 

 figaired b}^ Prof. E. J. Garwood from the ' Stick-Bed ' of D, age in 

 the North-Western Pi-ovince. Sections show this rock to be highly 

 crinoidal, and to contain abundant bryozoa and (?) Palecliinus 

 spines. 



S^ (h). (Thickness = about 6S feet.) — While these rocks are 

 predominantly dolomitized Litliostrotion limestones, there is a 

 good deal of variability. The following bands in the lower part 

 may be enumerated : — 



(i) Above the ' back slope ' is a band, about 11 feet thick, of dark dolo- 

 mitized limestone, containing basaltiform Lithostrotion associated with 

 Syringopora and Lithostrotion martini. The basaltiform Lithostrotion 

 shows np as white patches on the face of the rock. The position of 

 this layer, which is the Lithostrotion-aranea Band of Stoddart, is 

 shown in Vaughan's Avon paper, pi. vi. 



(ii) The ' front slope ' is a bedding-plane of shale covered with Seminula 

 ficoidea. 



(iii) Some 3 feet above the ' front slope ' is a shaly parting (A 104 a), 

 alluded to by Vaughan (Avon paper, p. 114) as the ' Trilobite-Bed.' 

 It contains numerous crushed valves and spines (PL X, fig. 5) of 

 Prodiictus semireticidatus associated with the bryozoan Heterotrijpa 

 of. tumida, with (?) Palechinus spines, and more rarely with pygidia 

 of a small PhilUpsia. The rock between this level and the ' front 

 slope ' is partly dolomitized limestone full of Seminula and Prodnctns 

 semireticidatiis. 



Only very thin shaly partings are seen in S^ above the ' Trilobite- 

 Bed,' and the series thenceforth consists of dark massive limestone, 

 much dolomitized, but not sufficiently so to cause obliteration of 

 the fossils. About 5 feet from the base of this series is the well- 

 known layer containing abundant Caninia hristolensis Vaughan, 

 associated with Lithostrotion. Foraminifera and brj^ozoa are also 

 abundant at this level. 



Large masses of Lithostrotion martini are a conspicuous feature 

 in the upper part of S^. Mr. E. B. Wethered^ hgures doubly- 

 terminated quartz-crystals formed by secondary growth from 

 detrital quartz, and describes them as abundant in the ' Middle 

 Limestone' (' Seminula Beds'), though occurring in both higher 

 and lower beds. Miss M. B. Chapman, ^ who records the presence 



1 Q. J. G. S. vol. xliv (1888) p. 192 & pi. viii, figs. 3-4. 



2 Geol. Mag. 1912, p. 501. 



