238 E. A. WALFOKK ON THE 



authors, a bed superior to the Upper Trigonia-grit of Leckliampton* ', 

 but is in fact the equivalent of the Lower Trigonia-bed." The 

 analysis of the table of fossils of the Hook-Norton limestone (C) in- 

 clines towards an agreement with the fauna of the zone of Ammonites 

 Parhinsoni. The affinity between the Clypeus-grit and series C 

 and D of Hook Norton is illustrated by the occurrence in both of 

 Trigonia producta and Am. Parhinsoni, as well as of such cosmopo- 

 litan forms as Pecten personatus, MyacitesGoldfussi, and Pholadomya 

 Heraulti. Another link in the chain of evidence is that Trigonia 

 signata has not been found in the Clypeus-grit of North Oxford- 

 shire, but appears sparely in the Hook-Norton Limestone, and attains 

 its maximum and dies out in the " signata'^ bed, into which the Hook- 

 Norton limestones probably merge. A noticeable feature, however, 

 is the restriction to the former bed of such abundant species as 

 Homomya gibhosa and Clypeus Plottii, neither of which appears to 

 have been found in either Hook-Norton or Chipping-Norton lime- 

 stones, though the passage of the latter species is demonstrated 

 by its appearance in the lower beds of the Great Oolite. Terebratula 

 globata, quoted by Prof. Judd from Otley Hill, I have recognized 

 doubtfully in a solitary specimen from Hook Norton. 



It appears as if this area, during the Lower Jurassic period, formed 

 a barrier which prevented the sea of the Clypeus-grit from ex- 

 tending into the north-east area, but was surmounted by the later 

 overflow of seas affected by the estuaries of the north-east ; and 

 so the Echinoclerms and MoHusca which characterize the grit died out 

 or migrated, being unable to adapt themselves to the new conditions. 

 The sea would seem to have receded after the deposition of the 

 early oolitic beds only to return after the filling up of the greater 

 part of the Cotteswold basin. There is evidence of considerable 

 denudation after the deposition of certain of the Lower Bajocian 

 beds and prior to the time of the Clypeus-grit, and again at about 

 the commencement of the Great-Oolite period. The former is 

 shown in the before- mentioned section at Salford, where the 

 Clypeus-grit can be seen resting unconformably upon the Upper 

 Lias, with the intervention here and there of the remains of a 

 compact freestone-bed covered by a thin ferruginous band. The 

 records of the second period are evident wherever the junction 

 of the Inferior with Great Oolite is shown. At Sharpshill (fig. 2), 

 Swerford, and Newbottle it is especially marked. 



Of the subsequent denudation by which the hills of North Oxford- 

 shire were in so many cases partially, if not wholly, stripped of their 

 limestone caps, and by which the soft outlines of the placid scenery 

 of the Midlands were sculptured, nothing need here be said. 



* "On the Subdivisions of the Inf. Oolite of the S. of England/' by Dr. 

 Wright, F.R.S. (Quart. Journ. G-eol. Soc. vol. xvi. p. 43). 



