OOLITE OP THE COTTESWOLD HILLH. 501) 



l^farl arc very small ; in the Upper Freestone they are nearly as 

 large as those in the Lower Freestone, and in the Kagstones we get 

 the largest size of any. 



EXPLANATION OF PLATE XX. 



Fig. 1. Section of coarse limestone from near the base of the Pea-Grit Series. 

 Shows it to be non-oolitic, and to be largely made up of the 

 ossicles of crinoids and fragments of other echinodermatii. X 12 

 diam. 



2. Section of coarse semi-oolitic limestone from the Pea-Grit Series, a 



few feet above the spot from which the specimen represented in the 

 previous figure was collected. It shows that some of the fragments 

 in the rock are coated with a crust made up of the tubules of 

 Girvane/la. These are illustrations of the oolitic granides which 

 appear in the beds. X 12 diam. 



3. Section of what may be termed an ordinary oolitic granule from 



Bed No. 20 of the Pea-Grit Series at Cieeve Hill. The figure shows 

 the granule as it appears in thin section, when simply polished, and 

 not covered with Canada balsam. It shows a dark granular 

 structure, with streaks and spots of calcite. The latter is infilling, 

 and the whole is suggestive of a tubular structure, the outlines of 

 which have been almost obliterated by molecular changes. X 70 

 diam. 



4. Siliceous casts of organic structures in the "Typical Pea Grit" at 



Stroud. X 48 diam. 



5. Grains of quartz from the Pea-Grit Series at the Horsepools, near 



Gloucester, x 18 diam. 



6. Microscopic quartz-crystals formed in situ. They are associated with 



flakes of silicate of alumina and cryptocrystalline silica, from which 

 they appear to have originated. X 40 diam. From Bed No. 5, 

 Pea-Grit Series, Cieeve Hill, near Cheltenham. 



DlSCTJSSION. 



Prof. Hull gladly acknowledged the great amount of labour evinced 

 by this paper on the part of the Author. When engaged many 

 years ago in the geological survey of the Cotteswold Hills, he (Prof. 

 Hull) had often felt the need there was for a microscopical exami- 

 nation of the Oolitic strata. Mr. Wethered had now supplied this 

 want in a district which had been so ably illustrated as regards its 

 palaeontology by his distinguished relative, the late Dr. Wright. As 

 regards the relations of the Upper Lias to the Inferior Oolite — as, 

 for example, at Frocester Hill, where Dr. Wright had opened out 

 his " Cephalopoda-bed " — it had always appeared to him that there 

 was a very marked line of demarcation between the Upper-Liassic 

 sands, with their peculiar fauna of ylmmoni<<?5, and the basement beds 

 of the Inferior Oolite ; but, as the " transition " strata described by 

 Mr. Wethered appeared to underlie the horizon of the Pisolite (or 

 Pea (irit), he thought it probable that the hiatus w^as to some extent 

 tilled up by them, and that his views might not, after all, be so 

 different as he had supposed from those of the Author. 



Mr. Etheridge was glad to find that the Author was continuing 

 his investigations into the petrological as well as the micro-zoolo- 

 gical structure of the Oolites of the Cheltenham or Cotteswold-Hills 

 area. The so-called " Transition Beds " between the sands of the 



