274 



ME. S. S. BTJCKMA^^ ON^ 



[vol. Ixxiii, 



Mr. Tutcher takes strong exception to the use of Arnioceras 

 to indicate a horizon, because it has too wide an extension, 

 ranging, he sa^^s, through most of the strata here placed as 

 Lymian. But the Dorset evidence shows Atviioceras dominant in 

 a particular set of beds ; and, although this may be striking because 

 of the absence of certain preceding strata, yet it is sufficient for 

 the present : there is a ^o^i- Agassiceras horizon with Arnioceras 

 shown at Raasay, and a ipre-birchi horizon with Arnioceras in 

 Dorset. A more suitable name for this faunal horizon must wait 

 until the many species of the genus are better known. It is quite 

 possible that here again may be faunal repetition. 



The following table gives the evidence of the various areas : — 



Dates. 

 Hemerse. 



Table VIII. — Ltmiain^ : Scotland and England. 

 Strata. 



Raasat. Yorkshire. 



Gloucestee- 

 shire ,2 etc. 



Bristol 



DlSTRICT.3 



Dorset 



COAST.-l 



hircM 



7. Arnioceras .. 

 6. Agassiceras .. 



4. vercingetorix . 



-3. bucMandi .. 



2. rotator 



X X Bredon, W. X Horfield. 



R. Up. BticJc- X Kadstock. 



landi [&]. 

 R. C Vp.BucJcUa]. X Bredon, W. Keynsham. 



I Mid. BucH. 

 X X Berkeley, W. Keynsliam. 



Mon. pi. iv. 

 Low. BiicJcL X Fretlierne, W. 

 [c]. Mon. pi. iii. 



Keynsham. 



Keynsham. 



1. Vermiceras ... 



Low. BucH. 

 [a]. Top 

 angulatus. 



C Keynsliam. 

 \ Sodbury. 



75 

 50-72 

 49? 



(40-47) ? 



C (26-29) ? 

 ■J X Wright, 

 CMon. pi. V, f. 



21 



1 See R, Tate & J. F. Blake, ' Yorkshire Lias ' 1876, pp. 58-62, suggested inter- 

 pretation. 



2 W., Wright's records in his ' Monograph of the Lias Ammonites ' (Pal. Soc). 



3 Mr. Tutcher's information, and a summary' of MS. sections which he has most 

 kindly allowed me to use. 



■* My interpretation of Mr. Lang's records, Proc. Geol. Assoc, vol. xxv (1914) 

 pp. 310 et seqq., and one of Wright's records. 

 [R. Strata in relative position. X In all cases, fauna present, position surmised.] 



The faunal sequence below the Sinemurian (Lymian) I leave in 

 the most capable hands of Mr. Tutcher, who has kindly contributed 

 what is placed as Appendix I, p. 278. He has also given his 

 reading of the lower part of the Sinemm-ian sequence, as he has 

 observed it in the Bristol district : this, too, I am pleased to record. 

 There are differences in our two accounts ; but, as they are records 

 of original observation and research, not statements for a text- 

 book, there is no need to strive for uniformity. Several differences 

 are merely details : he uses trivial names where I employ generic. 



