578 BEPORT— 1889. 



the town display about 40 feet of Jurassic strata, comprising upper and lower 

 Oxford clay, with Kellaway's Rock between ; cornbrash and great oolite limestone 

 separated by a considerable thickness of purplish clay. Measured against the 

 sombre hues of these clays, the tawny yellow of the Kellaway's rock shows to 

 advantage at this section. Where the sand has been dug away, doggers of large 

 dimensions, mushroom-like in shape, stand about, each as it were on a pedestal of 

 its own, or put out their rounded forms from amongst the sand in which they lie. 

 The outer coatings of these stones are loose, crumbly, and full of shells, while 

 their interiors are made of hard, calcareous sandstone, with a considerable pro- 

 portion of iron. The frequent occurrence of such hard masses amongst the sand 

 seems to arrest the percolation of water, so that springs (more or less ferruginous) 

 issue in the county that (judging by its protrusion hard by) must begin with the 

 dogger. Remarkable doggers are well exposed in the railway cutting at Oakley 

 Station on the main line from London to Leicester, where some of them measure 

 10 feet across and 30 feet in circumference. The doggers are merely locally 

 indurated lumps of sandstone, and the outcrop of the bed gives a white tinge in 

 dry weather to the fields on it, earning for them the name of ' The White Land ' 

 in the district. 



7. The Polyzoa of the Hunstanton Bed Chalk. By G. R. Vine. 



In this paper the author gave a bibliographical notice including 25 references, 

 and acknowledged the use of the collection in the Royal School of Mines. After 

 referring to the apparent poverty of a polyzoan fauna in some cretaceous rocks, he 

 proceeded to describe the polyzoa encrusting over a thousand specimens of fossils 

 from the collection of Mr. T. Jesson, F.G.S. After some remarks on classification, 

 figures and descriptions of 16 species belonging to the genera Stomatopora and 

 Proboscina, were given. 



MONDAY, SEPTEMBER 16. 

 The following Papers and Report were read : — 

 1. The Devonian BocJcs of Great Britain. By W. A. E. Ussher, F.G.S. 



The Devonian rocks of the south-west of England are divisible into three typical 

 areas, viz. the northern area, including North Devon and West Somerset; the 

 southern area, or South Devon ; the western area, including Devon west of Dart 

 moor, and Oomwall. The characteristics of these regions may be summed up as 

 follows : — 



Northern area : — Prevalence of arenaceous deposits indicative of shoal water and 

 proximity to coast, as pointed out by Dr. Kayser in a recent paper on the results of 

 a trip to North and South Devon under the guidance of the author. 



Southern area: — Great variability ; volcanic eruptions sporadic from the Eifelian 

 to the Fammenien and locally protracted (Ashprington volcanic series). Coral 

 reefs seem to have grown irregularly upward over considerable areas contempo- 

 raneously with muddy sedimentation beyond their borders. Arenaceous deposits 

 are confined to the Lower Devonian. 



The Western area displays more uniform conditions, as muddy precipitation 

 seems to have taken place almost uninterruptedly ; arenaceous deposits, with some 

 trivial exceptions, being confined to the lowest beds. 



As regards structure, that of the Northern area is simple ; but it is very dififerent 

 in the Southern and Western areas. Although cleavage and dip are often coinci- 

 dent in the slate districts, the frequent obliteration of planes of deposition justifies 

 great caution in interpreting structure by divisional planes. The crushing and 

 plication so manifest in the bedded limestones show us what to expect in the slate 

 areas. The persistence of direction of dip, where reliable, afibrds by no means a 



