loo 



M1J. S. S. BUCKMAX OX 



[vol. lxxvi, 



Mr. Richardson has produced many points for consideration, 

 but one more may he mentioned. Hitherto the Gloucestershire 

 Lias deposits have been considered as showing a fairly complete 

 and typical sequence. Now it may be seen that, in the middle of 

 what appears to be a quite conformable set of clays of the Middle 

 Lias, there is, between the subplanicosta horizon and the hronni 

 clays, a great gap in the sequence, during which there was 

 deposited in the Hebrides some 300 to 400 feet of strata and 

 above them another 100 feet or so in Yorkshire. Thus the gap 

 represents some 500 feet of strata, which is about half the 

 thickness, perhaps, of all the Middle and Lower Liassic strata of 

 Gloucestershire. Just the upper part of this gap may be filled 

 by the deposit some 30 feet thick yielding the brachiopoda dis- 

 cussed above, p. 71. Traces of a Pliricodoceras fauna and the 

 more or less local tubellum episode seem to point to the presence 

 of pockets of strata preserved in places ; and they suggest the 

 possibility that further research may reveal traces of some of 

 the faunal horizons of this big gap preserved in pockets, or more 

 or less remanies, in the area of the Severn Valley. 



(11) The following Table (XIV) gives my interpretation of 

 the datins; of the Gloucestershire-Worcestershire strata discussed. 



Table XIV. — Gloucestershire-Worcestershire Lias 

 Dating and Faunal Distribution. 



Strata with. Fauna. 



Oistoceras \Amblycoceras sp.] (23), Lytoceras (22), Androgyno- 

 ceras (21). 



Acanthopleuroceras solare, quadratum (20). 



Liparoceras cheltiense (19). 



Acanthopleuroceras valdani, etc. (18) 



Tragophylloceras spp. (17). ' 



Polymorphites \JTptonici) hronni (16). 



Rhynchonella thalia (15). Gloucestershire, Dorset ?, Xormandy. 



Cincta spp. (14). Gloucestershire, Somerset, Dorset, Normand\', 

 Wiirtemberg. 



Rhynchonella sp. \_rostellata] (13). Gloucestershire, Wiirtemberg:. 



Pliricodoceras.] 



Bifericeras tubellum (12). Dorset, Gloucestershire, Yorkshire. 



' Polymorphites polymorphic' (11). Bifericeras subplanicosta 

 (10). 



Microceras spp. (9). 



Cymbites globosus (8). Deroceras spp. (7). 



Echioceras spp. (6). 



Oxynoticeras guibalianum [Gleviceras ?] (5). 



Chellonia (4), Oxynoticeras oxynotum (3) + ' Pol. polymorphiisi' 



Bifericeras biferum group. Warwickshire ; Gloucestershire 

 (Aston Cross, near Tewkesbury, and Cheltenham) ; Somerset 

 (Canard's Grave, near Shepton Mallet) ; Wiirtemberg.] 



Oxynoticeras ferrvgineum [flavuni] (2). 



O. [Arietites~] cluniacensis (1). 



Lacunata horizon, Schlotheimia lacunata series, Schl. glevensis 

 series, Schl. cheltoniensis, Schl. rumpens. Yorkshire, Chelten- 

 ham, Gloucester, Rhone Basin, Wiirtemberg, Italy. 



Stibpolita horizon, Schlotheimia subpolita series. Yorkshire- 

 Cheltenham, Hierlatz.] 



Denotatus horizon. Arietites denotatus, etc. Yorkshire, Chel- 

 tenham, Wiirtemberg.] 



Ages. 





Hwiccian, 



5. 





2. 





1. 



Wessexian, 



10. 





9. 





7. 





?. 





?. 





? 





[1- 



Raasayan, 



4 b. 





2 b. 





2a. 





lb. 





la. 



Deiean, 



6. 





4. 





[3. 





2? 





1? 



Mercian, 



7 c. 





\1\>. 





\u. 



