IN THE ANGLO-PARIS BASIN 119 



(ii) THE SUBZONAL SEQUENCE (Table i, p. 10) 



(a) Subzone of Hoplites (Isohoplites) eodentatus 



Recognised by Casey (1961a ; 498), although few details were given on that 

 occasion, this index replaces the Subzone of Douvilleiceras inaequinoduni of Spath 

 (1923a ; 4 : 1923b ; 73 : 1941 ; 668). In England, the Subzone is represented in a 

 fossiliferous uncondensed state in the Isle of Wight (p. 52) and at Okeford Fitzpaine, 

 Dorset (54). Elsewhere, the known sections exhibit either unfossiliferous sediments 

 which probably represent this time span, or remanie phosphatic nodule beds. Future 

 deepening of the section at Small Dole, Sussex (p. 35) and at Badbury Wick, Wilt- 

 shire (p. 61) may provide a fossiliferous little-condensed sequence from which a direct 

 comparison can be made with the succession at St. Martin (p. 100). Maurupt (p. 89) 

 and Les Cotes Noires (p. 91) in France. Nowhere in England are the sections at the 

 outcrop in this subzone particularly fossiliferous. 



In England, the ammonite fauna consists essentially of species of Hoplites (Iso- 

 hoplites) of which H. (I.) eodentatus is typical. It is necessary to bear in mind that 

 the tendency to produce the peripheral rib pattern of a typical Hoplites (H.) men- 

 tioned already, can be so well advanced that a fragment or even a complete individual 

 would have to be referred to Hoplites (H.). This fact alone shows the artificial nature 

 of the subgenus Isohoplites. However, these are associated with species in which 

 the Pseudosonneratia ventral aspect is still well developed. Apart from the forms 

 derived from Pseudosonneratia, there are other Hoplites derived from Otohoplites and 

 possibly Protohoplites , and in fact rare specimens of Otohoplites still occur. The 

 associated ammonites include Beudanticeras such as B. laevigatum, B. albense, and B. 

 santaecrucis, together with Douvilleiceras spp. including D. inaequinoduni. 



Lyelliceras of the camatteanum type, which stands rather in the same relationship 

 to Tegoceras on the one hand and Lyelliceras of the lyelli type on the other, as does 

 Isohoplites in the hoplitinids, is a great rarity in England. In France it is a reason- 

 ably constant and characteristic companion of Hoplites (Isohoplites) and the other 

 ammonites mentioned above, and this has led P. & J. -P. Destombes to recommend 

 that the Subzone be denned as that of Tegoceras camatteanum and Isohoplites 

 eodentatus (1965 ; 265-6). They indicate a type locality, Les Cotes-Noires pres de 

 Moeslain, where the subzone is represented by clays in an apparently unbroken 

 sequence from the top of the mammillatum Zone to the base of the lyelli Subzone. 

 In the lower clays classified with the eodentatus Subzone there is the association of 

 Hoplites (Isohoplites) eodentatus and Lyelliceras camatteanum as there is also at 

 Maurupt and St. Martin. If one wishes to use a double index then this emendation 

 proposed by P. & J. -P. Destombes should be adopted. However, as H. (I.) eodentatus 

 is common to this time span throughout the Anglo-Paris basin, the writer employs 

 this index only. 



(b) Subzone of Lyelliceras lyelli 



P., & J. -P. Destombes (1965 ; 265-7) have formally proposed that the benettianus 

 Subzone in Spath's sense should be redefined as the Subzone of Lyelliceras lyelli & 

 Hoplites benettianus. So, the tentative suggestion of Barrois, the bald statement of 



