IN THE ANGLO-PARIS BASIN 123 



the spathi Subzone is well represented by forms such as E. loricatus, E. microceras, E. 

 subtabtdatus and E. pricei. Early forms of Dimorphoplites including D. niobe 

 (praemutation) occur sparingly, and some of these show a tendency to the lautiform 

 ribbing not generally developed again in the genus until the meandrinus Subzone. 

 Heteromorphs are not uncommon and consist not only of Hamites (H.) spp., but also 

 of species of Protanisoceras (Heteroclinus). The early binneyitid Falciferella mil- 

 bonrnei can be abundant at certain horizons. Apart from the endemic forms, there 

 is a much rarer element represented by specimens of Uhligella, Tetragonites, Des- 

 moceras, Eubrancoceras and Pseudhelicoceras (e.g. P. subcatenatum Spath.) 



The upper limit of the Subzone is marked by the quite sudden decline of Ana- 

 hoplites of the intermedhis group, which do not extend into the niobe Subzone above. 



(e) Subzone of Dimorphoplites niobe 



The Subzone was recognised by Spath (1924 ; 505), it having previously formed 

 part of his intermedins Zone (1923a, b). It has been considered to be of local value 

 (Spath 1942 ; 672) but in fact it is of widespread occurrence. Sediments of this time 

 span are relatively uncondensed at Folkestone and to a lesser extent at Small Dole. 

 Elsewhere in the Weald the sequence is somewhat condensed, where indeed it has 

 escaped basal Upper Albian planation. Outside the Weald, it is developed in the 

 Leighton Buzzard district. In France, the Subzone may be developed at Wissant 

 (p. 83), but the only locality at which it can be proved with certainty is Cauville, 

 Seine Maritime (p. 107). The restricted development of the niobe Subzone led Breis- 

 troffer in effect to include it in the intermedins Subzone (1947 ; 44, 1965 ; table 

 opposite p. 312) but his view was probably also influenced by Spath (1942 ; 672). 



The ammonite fauna is a curious one in that it has no species restricted to it, yet 

 it is distinctive. Anahoplites intermedhis and its allies have gone, and Dimorphoplites 

 niobe, A. planus and A. splendens are the characteristic species. The upper limit 

 of the 'Subzone occurs immediately below the appearance of Mojsisovicsia in the 

 sequence. 



(f) Subzone of Mojsisovicsia subdelaruei 



Originally indexed by Spath (1923a ; 4, b ; 73) using ' Dipoloceras ' delaruei. He 

 realised later that this species did not occur in this time span, and it has been found 

 subsequently in the spathi Subzone. The Subzone as originally defined included 

 sediments now classified with the meandrinus Subzone. The Subzone is represented 

 by uncondensed deposits at Ford Place, Wrotham (p. 22) and at Sevenoaks (p. 25), 

 but elsewhere in England where deposits of this age are preserved they are condensed. 

 In France, they are known only in a condensed state (e.g. Bed 11 at Wissant). 



Apart from the species of Mojsisovicsia, a genus which last made its appearance 

 in the Anglo-Paris basin in the spathi Subzone, and which in the subdelaruei Subzone 

 shows marked evolutionary changes, the hoplitinid fauna shows more diversity of 

 form than in the niobe Subzone below. Mojsisovicsia subdelaruei appears at the 

 base of the Subzone and evolves to M. remota at the top. The occurrence of Dimor- 

 phoplites niobe led Milbourne to unite this time span with the niobe Subzone (1956 ; 

 241, 1963 ; 64), but on balance this incursion of keeled ammonites into the Anglo- 



