46 GASTEROPODA OF THE INFERIOR OOLITE. 



massive and partly ironshot limestone, full of keeled Ammonites, many of which, 

 belong to the concavus group. Terebratula perovalis, var. ampla, is characteristic 

 of the higher block. Mr. Whidborne has obtained a few good Gasteropoda from 

 here, which appear to me to have been procured from the concavus-bed or beds. 

 These then belong to the Lower Division. 



A few inches of rather fossiliferous brash, with many Astarte obliqua, separates 

 the concavus-beds from the undoubted Parlcinsoni-beds. Very large specimens of 

 the var. Dorsetensis are obtained from the lowest beds, which also have yielded a 

 few Gasteropoda. A great physical change comes on here in the thickening of 

 the Upper Limestones above the main fossil-bed, the total thickness of limestone 

 exceeding thirty feet, which is very different to anything hitherto noted, where 

 the usual thickness of the Inferior Oolite Limestone has not much exceeded 

 twelve feet. 



Louse Hill. — This place is near Halfway House. I have not been to it myself, 

 but there is said to be a thin ferruginous bed which yields fossils of the 

 Hump>hriesianus-zone. I have a great many specimens of Pleurotomaria from here, 

 but few if any are fit for figuring. 



Sherborne. — Two and a half miles east of Halfway House. There are several 

 quarries, especially towards the north-west of the town, where the Inferior Oolite 

 has been worked. Immense numbers of Ammonites have been obtained from 

 these, and from excavations for houses. More than one zone is well developed, but 

 as I have few if any Gasteropoda from here, a detailed description would be super- 

 fluous. The fossils show that there is a rich development of the Humphriesianus- 

 zone, but the bulk of the limestones, nearly forty feet thick altogether, are in the 

 ParJcinsoni-zone, which has yielded lately a splendid specimen of Megalosaurus Buck- 

 landi, von Meyer. Speaking generally, however, the neighbourhood of Sherborne, 

 especially Oborne and Milborne Wick, is famous for a good development of the 

 Humphriesianus-zone. Indeed, this immediate neighbourhood is the only one in 

 the Dorset- Somerset District where beds of that age occur to any extent. 



Oborne (Frogden Quarry). — If Burton Bradstock gives us the Gasteropoda of 

 the Parkinsoni-zone to perfection, if Bradford Abbas is still more famous for the 

 Gasteropoda of the Murchisonee- and Sowerbyi-zones, in this quarry we possess the 

 best example which England affords of the beds of Bayeux — the " oolithe ferru- 

 gineuse," which is mainly characterised by Stephanoceras and Spharoceras — in 

 other words, the zone of Am. Humphriesianus. The traveller from Normandy by 

 the route we have taken might well wonder what had become of D'Orbigny's 

 typical Bajocian, but here it is at last. 



Beginning from the base as usual, we note that the Lower Division of the 

 Inferior Oolite is not represented by fossils in this quarry, though it is probably 

 represented by some of the massive series of calciferous grits, which extend for a 



