﻿Vol. 6l.] SEQUENCE IN TKK BKISIOL AliKA. 305 



Plate XXV, 



Figs. I & la. Productus bassus, sp. nov. Convex valve ; X 1*6. 



K x subzone ; Avon section, Leigh Woods (Somerset.) 

 Figs. 2 &2a. Productus cf. Martini (Sow.). 1 Convex valve ; natural size. 



Zapkrentis-Zone ; Moat-House Quarry, west of Failand, near 

 Bristol (Somerset). 

 Fig. 3. Productus 9. Convex valve ; natural size. 



S] subzone; Great Quarry, Avon section, Clifton, Gloucester- 

 shire (Stoddart Coll.). 

 Figs. 4-4 b. Productus Cora, d'Orb., Davidson, mutation. 



Convex valves of two examples ; natural size. 

 Fig. 4. The form characteristic of the S 2 subzone. S 2 subzone ; Great 



Quarry, Avon section, Clifton (Gloucestershire). 

 Figs. 4a & 4 5. Variety with very fine ribbing. L\ subzone; Avon 

 section, Leigh Woods (Somerset). 

 Fig. 5. Productus hemisphericus, J. Sow., var. Convex valve ; natural size. 

 D x subzone; Sodbury (Gloucestershire). 

 (Variety with coarse ribs and narrow beak.) 



Plate XXVI. 



Figs. 1 & 2. The circulus of C'konetes cf. hardrensis, Phil. 



Fig. 1. Chonetes cf. laguessiana, de Kon. Convex valve ; natural size. 



Z x subzone ; Burrington section (Mendips), near Wrington 

 (Somerset). 

 2. Chonetes cf. crassistria (M'Coy). The two valves ; X 1*2. 

 Horizon j3 ; Failand section, near Bristol (Somerset). 

 Fig. 3. Chonetes aff. papilionacea, Phil. Convex valve ; natural size. 



Base of Syringothyris-Zone ; Cromhall, near Wickwar (Glou- 

 cestershire). 

 (One of the early papilionaceans.) 



4. Chonetes aff. comoides (J. Sow.). Convex valve ; natural size. 



D l subzone; Sodbury (Gloucestershire.) 



5. Spirifer aff. clathratus, M'Coy, Vaughan. Pedicle-valve ; natural size. 



Z x subzone ; Failand section, near Bristol (Somerset). 

 (The transverse variety.) 



6. Spiriferina octoplicata (Sow.), var. A slab showing several specimens ; 



natural size. 

 Horizon /3 ; Walton Castle, near Clevedon (Somerset). 

 (J. W. Tutcher coll.) 

 Figs. 7-7 h. Camarotcechia mitcheldeanensis, sp. nov. Natural size. 

 (Cleistopora-zone) ; Mitcheldean (Gloucestershire). 

 (Museum of Practical Geology, Jermyn Street.) 



Plate XXVII. 



Vertical sections showing the thickness and lithology of the zones and sub- 

 zones in the Carboniferous Limestone of the Bristol area, on the scale of 

 250 feet to the inch ; horizontal section of the Avon Gorge, on the scale of 

 500 feet to the inch ; and sketch-map of the quarries there. 



Plate XXVIIL 

 Kange-diagram of Carboniferous corals in the Bristol area, facing p. 244. 



Plate XXIX. 



Range-diagram of Carboniferous brachiopods in the Bristol area, facing 

 p. 246. 



1 Productus Flemingi (Sow.) var. burlingtonensis, Hall ('Palgeont. of N.Y.' 

 vol. viii, pt. i, pi. xviii, figs. 6-8) is probably identical with Pr. cLMartivi 

 and occurs at the same horizon, namely, in the Burlington Limestone. 



