Vol. 55.] GREAT CENTRAL RAILWAY : RUGBY TO CATESBY. 69 



was above the semicostatus-zone and below the ox i/notus -zone, there 

 could be little doubt that it represented the ohtusus-zone, though for 

 a long time no direct evidence was forthcoming in support of the 

 propositiou. At the Hillmorton & D unchurch Eoad bridge, between. 

 K and L, about 7 feet of this clay was exposed, but its total thick- 

 ness may be estimated at about 20 feet (see fig. 1, p. 66). 



I^ow, although the main mass of the bed was so very uninteresting, 

 the lower part of it made some amends as the cutting was deepened 

 in a northerly direction, for towards the place where fossils of the 

 semicostatus-zone occurred, and where blue Boulder Clay rested 

 directly upon it, several fossils characteristic of the obticsus-zone 

 were found. 



In the lower part of the Boulder Clay hereabouts there was a 

 line of large blocks of blue limestone, which extended almost as a 

 continuous bed for some distance on each side of the bridge at I, 

 though the large blocks composing it were at very different angles 

 with the horizon and each other, and many were smoothed and 

 scratched. Some of these blocks immediately north of I, and 

 nowhere else, contained enormous specimens of Ammonites obtusus, 

 others A. semicostatus, A. Sauzeanus, Gryphcea spp., Lima gigantea, 

 etc. ; and this is just about the place where the northward-dipping 

 Boulder Clay would naturally truncate both the ohtusus- and semi- 

 costatus-zones (see fig. 1, p. 66). 



The following, among other characteristic fossils, were obtained : — 

 Ammonites Birchii, Sow. ; A. ohesulus, Blake ; A. lacunatus^ Buckm. ; 

 A. ohtusus, Sow. ; and A. stellaris, Sow. 



{c) Zone of Ammonites oxynotus (figs. 1-2, pp. QQ> & 70). 



The oxynotus-zone is exceedingly well developed, and was clearly 

 exposed on either side of the line, both north and south of the 

 Hillmorton & Dunchurch Road bridge, between 53 miles 55 chains 

 and 54 miles 20 chains. There was no essential difference between 

 the clay of this zone and that of the zone below, nor could any 

 lithologioal boundary be made out, yet fossils become almost sud- 

 denly quite numerous. Ammonites, belemnites, Gryphcea cymbium, 

 and Hi ppojpodium, ponderosum are very abundant. The section near 

 the bridge is approximately as below : — 



Feet. 



Gravel 8 



Zone of Ammonites armatus 5 



Zone of A. oxynotus 25 



Zone of A. obtusus , 7 



45 



There is a nearly continuous band of limestone extending along 

 the cutting in the midst of the oxynotvs-zone, and at the same 

 inclination ; it is very largely made up of Gryphcea (cymbiuml). 



The clay of this zone is blue, and by no means highly charged 

 with iron-pyrites or iron-peroxide, as it appears to be in some 



