122 MIDDLE ALBIAN STRATIGRAPHY 



The division between the lyelli and spathi Subzones has been discussed above. The 

 sediments representing the transitional period between the spathi and intermedins 

 Subzones do not contain ammonites in the area of the Weald except at Petersfield 

 (p. 34). At present it cannot be demonstrated in any one section in England, how- 

 ever, the section at Osmington (p. 51), Dorset, and Caen Hill, Devizes (p. 60) show 

 the extreme top of the spathi Subzone and the extreme base of the intermedins Sub- 

 zone respectively. Bed 2 at Osmington contains abundant high spathi Subzone 

 Hopiites (H.) together with rare early forms of Anahoplites of the intermedins group 

 such as A. osmingtonensis and A. grimsdalei spp. nov. In Bed 7 at Caen Hill, 

 Hopiites (H.) has become very subordinate to slightly later forms of Anahoplites such 

 as A. evolutns which are in turn earlier than Anahoplites intermedins and its con- 

 temporaries. A . evolutns is also known from Bed C at Hunstanton. These sediments 

 containing A. evolutns are here considered to mark the base of the intermedins 

 Subzone. 



In France, fragments of Anahoplites osmingtonensis and A. evolutns occur in Bed 4 

 at St. Florentin (p. 97), a phosphatic nodule bed containing en melee material derived 

 from both the spathi and intermedins Subzones. At Revigny-sur-Ornain (p. 88) 

 these transitional sediments are uncondensed but the ammonites are mainly crushed 

 flat. At Wissant sediments deposited during this period have not yielded ammonites. 



There is no difference between this interpretation of the spathi Subzone and the 

 views of French geologists (e.g. Breistroffer 1965 ; 313). From this account it is now 

 obvious that the parochial view expressed by Milbourne (see Hancock 1965 ; 246-7), 

 fixing the top of the spathi Subzone at an horizon of condensation in a comparatively 

 small area of the outcrop in the northern Weald, is totally unacceptable. The record 

 of Anahoplites intermedins a foot or two above the spathi nodule bed at Folkestone 

 (Bed I (vi) ) by Casey (in Hancock 1965 ; 247) is here considered to be a misidentifica- 

 tion of the finely-ribbed H. (H.) dentatus densicostata Spath which is just as common 

 in the higher part of the Subzone. 



(d) Subzone of Anahoplites intermedins 



Although there is some condensation at Folkestone, this section (p. 14) provides the 

 best sequence yet known in this Subzone recognised by Spath in 1923. The sequence 

 at Small Dole is the least condensed and also shows, albeit imperfectly, the junction 

 with the spathi Subzone below, and also the junction with the niobe Subzone above ; 

 however, the fauna is crushed flat. The junction with the spathi Subzone has been 

 discussed above. The lowest part of the Subzone with Anahoplites evolutns has not 

 yet been discovered in the Weald and so at Folkestone the earliest intermedins Sub- 

 zone sediments containing ammonites yield Anahoplites intermedins and A. praecox. 

 In France the section at Wissant shows an imperfect development of sediments 

 representing this Subzone, but at Revigny-sur-Ornain, and at Courcelles the lower 

 part is well developed. 



The characteristic ammonites of this time span are the group of Anahoplites 

 typified by A. intermedins. The ammonite fauna of the Subzone as a whole is more 

 diverse than that of the spathi Subzone below. Hopiites (H.) is greatly subordinate 

 to the other genera, but the group which had produced rare Euhoplites by the top of 



