i->.| MIDDLE ALBIAN STRATIGRAPHY 



Paris basin dictates that it be kept separate. The species of Euhoplites show little 

 difference to those of the niobe Subzone below, but Dimorphoplites commences to 

 differentiate towards the forms seen in the meandrinus Subzone above. 



The upper limit of the Subzone coincides with the last appearance of M. remota. 

 However, Mojsisovicsia is not at all common at this height and it is necessary to use 

 the grade of development shown by the species of Euhoplites and Ditnorphoplites at 

 the base of the meandrinus Subzone, discussed below. 



(g) Subzone of Euhoplites meandrinus 



This time span, included by Spath in his subdelaruei Subzone, was indexed by 

 the writer (Owen i960 ; 373, 376). Its separate nature was recognised by Milbourne 

 (1956 ; 241), who included it provisionally in the nitidus Subzone, and by the author 

 (Owen 1958 ; 162). Unfortunately, there is an error in Hancock (1965 ; 245 Table I) 

 for this Subzone was not included by me in the nitidus Subzone, that is, in the basal 

 Subzone of the lautus Zone as restricted by me in 1958. Milbourne (1963 ; 65) 

 indexed this Subzone with his ' species ' Euhoplites neglectus (which on examination 

 of the type material proves to be a synonym of E. meandrinus) together with Dimor- 

 phoplites doris. My objections to this emendation were set out in Hancock (1965 ; 

 247) and this clash of opinion led to a mistake in the zonal scheme given by Kaye 

 (1965 ; 220). 



The Subzone is characterised by E. meandrinus and closely related forms such as 

 E. cantianus, E. loricatus (late mutation), and E. beaneyi which still possess the 

 deeply sulcate venter characteristic of the genus in the preceding subzones. The 

 late mutation of E. subtuberculatus tends to show the development of the channelled 

 venter characteristic in the lautus Zone on its outer whorl, but the inner whorls are 

 still sulcate. The pattern of ribbing on most of these species is transitional to that 

 of the typical lautus Zone species. Dimorphoplites has become more diverse in form 

 and apart from the typical meandrinus Subzone species such as D. doris and D. pinax, 

 there are the early mutations present of the species which occur commonly in the 

 lautus Zone above but they are greatly subordinate in numbers. Mojsisovicsia is 

 absent from this time span. 



In England, the meandrinus Subzone is present in an uncondensed sequence at the 

 Horton Clay Pit, Small Dole (p. 40). At the Sevenoaks Brick Works (p. 25) and 

 further east in Kent, the sediments are condensed to a variable extent. Its known 

 representation is confined to eastern England. In France, the only locality at which 

 the Subzone is known to be represented at this time is at Wissant in Bed 11 which 

 also contains material derived from subdelaruei Subzone sediments and nitidus Sub- 

 zone sediments as well. 



At Small Dole, and at Ford Place, in particular, the sudden change from a sulcate 

 to a channelled venter in the species of Euhoplites can be well seen in sediments which 

 are uncondensed. This marks the base of the overlying nitidus Subzone. 



(h) Subzone of Euhoplites nitidus 



Spath originally included Beds V-VII at Folkestone in a zone of Dipoloceras 

 cornutum (1923a ; 4, b ; 73) but having realised the rarity of that species he divided 



