270 MR. s. s. BUCKMAN ON [vol. Ixxiii, 



{^Oxpioticeras poly opliy Hum Simpson sp., 'Yorkshire TjqDe Am- 

 monites ' 1909, No. 8) may be worked out on theoretical grounds. 

 If it were placed immediatelj" above siinjjsoui, then the Yorkshire 

 strata would be in sequence ; but the biological features of 

 O. 2yol//02)ht/llum seem certain!}^ to suggest that it is a derivative 

 of O. oxijnotum with a suture-line of the same pattern, but 

 details somewhat more elaborated, and with ribbing greatly in- 

 tensified (renewed costation). In that case it should occur later 

 than O. oxjinotum, and, as there is no stratigraphical evidence to 

 go upon, it seems advisable to work upon the basis of the bio- 

 logical interpretation. This, however, involves a theor}^ of a non- 

 sequence in the Yorkshire Deiran deposits, and the multiplication 

 of non-sequences is inadvisable unless there be some evidence. 



The sequence thus suggested for the noticeably dissimilar oxycone 

 faunas of the different areas makes Yorkshire to show early Deiran 

 deposits with a middle Deiran fauna separated by a break ; 

 Gloucestershire, to which the Midlands may be joined, to show 

 middle Deiran faunas with, perhaps, a break in some localities due 

 to removal in places of deposits of polyopliyllum date : this would 

 account for local appearances and absences of the species in this. 

 area ; Somerset north of the Mendips to show late Deiran fauna, 

 with little deposit and certainly a good deal of redeposition. 

 Dorset shares with G-loucestershire an oxj^cone fauna of Glevicercn:: 

 date ; but its special form, 0. lymense, is not found m the other 

 British areas, so far as I am aware. Both these forms are pre- 

 sumably derived and redeposited in Raasayan strata; for, if 

 O. lyniense were indigenous in Bed 92, it ought to have been found 

 in the Raasayan deposits of other areas. The supposition, then, is 

 that a Jymense horizon is the latest phase of Deiran. 



Much support for the general conclusions here advanced about 

 the dissimilar faunas of the Deiran horizons ma}" be found in 

 Continental works : the Rhone Basin (Dumortier) sliows only 

 ammonites of the horizons Gagaticeras^ Gleviceras, and IRad- 

 stockiceras — those of the other horizons are lacking, for the 

 examples figured as A. oxynofus by Dumortier are species of about 

 the Gragaticeras horizon ; Wiirtemberg (Swabia, Quenstedt) shows 

 the oxynotum and biferum faunas certainly, doubtfully the Glevi- 

 ceras fauna, but no fauna of the others. 



Thus Gloucestershire and the Midlands are to be bracketed with 

 Wiirtemberg so far as the oxynotum fauna is concerned, and 

 are separable from other English areas ; Radstock, with its varied 

 and remarkable oxynotes. agrees with the Rhone Basin ; it shows 

 special forms not yet found in other British areas — the ^ad- 

 stoclticeras fauna. Yorkshire shows many oxycones which seem 

 to be peculiar to itself : it has little agreement with other English 

 .areas or with Wiirtemberg, but rather more with the Rhone 

 Basin — not, however, on the same basis as Radstock. 



Lastly, Dorset shares with Gloucestershire a little, but has 

 O. lymense to itself. (For further remarks see fig. B, p. 272, and . 

 also p. 273.) 



