202 A. R. Cox and A. E. Trueman— 



records no attempt lias been made by authors to identify the 

 Dactyliocerates of this zone, but as the deposits are frequently 

 paper shales, and constitute the lower part of the " Fish Beds ", 

 or Dumbleton Beds of Professor Judd,^ it can generally be identified 

 from descriptiozis of the sections." 



It has been shown by Mr. Buckman and others that the 

 tenuicostatuni zone attains its maximum thickness in Yorkshire, 

 is thick in Lincolnshire, and thence southwards is recognizable as 

 a very thin layer.'^ But this generalization is upset by a sudden 

 thickening of these beds along the Bredon syncline, for at Dumbleton 

 they are extremely well developed, a fact which further suggests 

 the existence of a basin there in Liassic times. 



As the teniiicostatum zone is traced southwards from Lincolnshire, 

 in those districts where a sufficient number of thicknesses is available, 

 further indications are obtained of intra-Liassic movement ; this 

 again appears to have occurred along the axes that have been 

 ])reviously noticed. There is, for instance, a slight thickening in the 

 Old Dalby syncline, although the zone generally is rapidly thinning 

 out southwards. The probable absence of the zone in the district 

 around Weedon near the Weedon anticline is interesting, as the zone 

 is certainly present at Chipping Warden and further to the south- 

 west. The zone once more thins towards Banbury, and Mr. J. 

 Pringle informs us that he believes it to be absent just north-west 

 of Banbury, where the overlying exaratimi zone, itself attenuated, 

 rests with a non-sequence on an inconstant representative of the 

 aciitiim zone which fills small liollows in the underlying Marlstone. 

 There was, therefore, but little deposition over this region during a 

 period in which deposits belonging to several zones were accumulating 

 elsewhere. Still further south-west, paper-shales occur at Chipping 

 Norton in the Edgehill syncline, but thin out once more towards 

 the line of the Moreton anticline, only to thicken in the Bredon 

 syncline, as we have already indicated. 



The results obtained from our study of the acutum and tenui- 

 costatuni zones are summarized in the table on p. 203, in which it 

 is seen that the variations in these two zones take place at exactly 

 those localities where they would be expected if the folding which is 

 indicated by the course of the outcrojos was in progress during the 

 jjeriods of deposition. In each case the deposits thicken towards 

 the synclines and thin away towards the anticline. 



(3) Other Zonal Evidence. — While it is not yet possible to follow 

 other zones in similar detail across the whole of the Midlands, there 

 are certain zones traceable for short distances which afford further 

 evidence of some of the supposed intra-Liassic movements. 



^ Judd, The Geology of Rutland, etc. (Mem. Geol. Surv.), 1875, p. 83, etc. 



^ Although in some of our figures, perhaps a portion of the exaratimi zone 

 may also be included. 



^ Buckman. " Certain Jurassic (Lias-Oolite) Strata of South Dorset, etc." ; 

 Quart, Journ, Geol. Soc, vol. Ixvi, 1910, p. 88. 



