OF NORTH OXFORDSHIRE AND THE CLYPETJS-GRIT. 243 



Notes and Corrections (14th April, 1883). 



Some little confusion has been caused by the variable conditions 

 affecting the lower beds A and B of the Hook-Norton series. 

 Whilst some new exposures show them to rest unconformably upon 

 the Upper Lias, attaining at the south end of the cutting a thickness of 

 5 feet 6 inches, and passing in places into a compact blue sandy 

 limestone, at the north end, and in the adjacent Duckpool-Farm 

 cutting, they are absent altogether. Both at Hook Norton and 

 at Otley Hill Rhynchonella cynocephala is found at the top of A, 

 together with Trigonia striata, T. Brodiei, Terebratula trilineata, 

 Pholadomya Jidicula, Monilivaltia cf. lens, &c. It is probably the 

 superior bed B which has yielded Ammonites Murchisonce, its variety 

 corrugata, and another form like Arnm. variabilis. It would seem, 

 therefore, as if we had in the lower part of the series an equivalent 

 of the " cynocephala " stage of Dr. Lycett, thus confirming my 

 surmise as to the existence of lower Inferior-Oolite beds over the 

 region, and perhaps, in part, representing also Professor Judd's zone 

 of Ammonites Murchisonce. 



Reposing upon the series mentioned, and just now admirably 

 shown at Otley Hill (vide Section, fig. 4, p. 244), is a band of hard, com- 

 pact crystalline limestone, curiously waterworn both above and below, 

 and measuring but 1 foot 4 inches in thickness. The great erosion 

 it has suffered prior to the deposition of the overlying marls is at 

 once apparent ; and it seems to be the dividing line between the 

 lower and upper Inferior-Oolite divisions. The coral-bed at Hook 

 Norton, which I had previously, in error, placed at the top of A, is 

 its equivalent, and is not only filled with concretionary or derived 

 fragments, but is bored and worn at the top. Large masses of 

 Isastrcea serialis occur in it, accompanied by Clausastrcea Conybeari, 

 Terebratula perovalis, &c, with Trigonia producta and T. angulata 

 on its upper surface. 



Discussion. 



Mr. Hudleston bore testimony to the value of the work done 

 by collectors in the neighbourhood of Banbury, both in the Lias 

 and Inferior Oolite. The latter was especially difficult to interpret 

 in North Oxfordshire, which was the border land between the South- 

 western or Gloucestershire types and the North-eastern or Nor- 

 thamptonshire types. He remarked on the confusion which had 

 been produced by the use of the term " Northampton Sand " as ap- 

 plied to beds in this district, since the real Northampton Sand re- 

 presents the zones of Amm. opalinus and Amm. Murcliisonai, whilst 

 at Chipping Norton its Oxfordshire namesake overlies the Clypeus- 

 grit, which is in the zone of Amm.. Parlcinsoni. Apart from the 

 question of names, the relations of the Clypeus-grit to the general 

 mixture of sandy limestones was a puzzle to which Mr. Walford's 

 careful observations afforded a clue of great importance. 



Prof. Judd stated that the intricacy in the geology of the district 

 was the result of the rapid thinning-out in passing north-eastward 



Q.J.G.S. No. 154. s 



