Vol. 55.] GEOLOGY or THE GEEAT CEI^TRAL RAILWAY. 77 



The nodules, although exceedingly abundant, are on the whole 

 small, or of only moderate size, and mostly very smooth except for 

 the fossils sticking out of them. They are light-coloured like the 

 clay (never red as in the beds above), and in and upon some of these 

 specimens of Rliynclionella were nearly as abundant as, and in better 

 condition than, in the clay. Practically all the fossils recorded 

 came from the nodules. 



No doubt these beds belong to what is usually known as the 

 Jamesoni-zoue ; but since there are apparently three very distinct 

 dejjosits between the armatus-zone and the ibex-zone, of which 

 this is the middle one, and it does not yield A. Jamesoni, I have 

 ventured to indicate it by the name of its characteristic ammonite, 

 ' pettos-zone.' The other specially characteristic fossils which I 

 obtained were : — Ammonites striatus, Eein. (a small specimen on 

 the same nodule with A. pettos) ; A. Oppeli, Schl. ; and Amherleya 

 Jidia, d'Orb. 



Besides the fossils, peculiar elongated — rod-like or branching — 

 pieces of iron-pyrites were very abundant ; there was also some 

 specular iron in the nodules. Some of the nodules were bored. 



{h) Zone of Ammonites Jamesoni (Upper Part). 



Eather less than 1| mile south of the Willoughby cuttings, at 

 58 miles 55 chains, immediately after crossing the Oxford Canal, a 

 small cutting begins, and extends for about 12 chains (see fig. 4, p. 74 ). 

 Its greatest depth is about 15 feet, and the material is a brownish 

 clay with ferruginous nodules and much selenite, which appears 

 to be absent in all the other sections. 



I found nothing here by which the zone could be identified, 

 though since the next cutting southward is at a higher level, and 

 consists of the ibex and Henley i- zones, one would naturally expect 

 the beds to belong to the Jamesoni-zone. Mr. H. B. Woodward 

 says ^: — ' Succeeding deposits comprise clays with ferruginous bands 

 and selenite, with small, flat, ferruginous cement-stones. Crossing 

 the Oxford Canal at Wolfhamcote these clays are found to yield 

 Ammonites Jamesoni, Belemnites, Plicatula spinosa.' 



The presence of Ammonites Jamesoni of course identifies the zone, 

 and the great dissimilarity between the beds and those of the zone 

 described in the foregoing section (g) of this paper aff'ords an 

 additional reason for giving the latter a distinctive name. 



(i) Zone of Ammonites ibex (fig. 4, p. 74). 



In the deep cutting east of Plecknoe and south-east of Nethercote, 

 extending from 59 miles 25 chains to 59 miles 52 chains, there 

 may be parts of three zones — ibex, He^ileyi, and capricomus, though 

 personally I detected only the two former. 



The cutting has a maximum depth of 40 feet, and when nearing 

 completion, in the lowest part towards the southern end, and for 



1 Geol. Mag. 1897, p. 98. 



