50 GASTEROPODA OP THE INFERIOR OOLITE. 



which is enormously rich in large Cephalopods, though not quite so good for 

 Gasteropoda as the top and bottom beds of the series. 



In the Department of Calvados there is a third bed where the ferruginous Oolites 

 become scarce and less well denned. This is characterised by the abundance of 

 Am. Niortensis and Am. Parkinsoni interruptus, by large varieties of Pleurotomaria 

 mutabilis, by PL bessina and PI. scalaris, and by " Turbo " duplicates. Specimens of 

 Terebratula splmroidalis are more abundant than in the second bed, and Ter. Phil- 

 lip sii may be noted. This description probably fits better with our Cadomensis- 

 bed (H 3 ) than either of the other two with their presumed equivalents. The abund- 

 ance of the peculiar group of Gosmoceras indicated by Am. Niortensis and Am. 

 Parkinsoni interruptus is very suggestive, since this is exactly what we find in H 3 

 at Oborne. Just as coming events cast their shadows before, so did these pre- 

 cursors of the grand army of Gosmoceras prepare the way for the reign of Am. 

 Parkinsoni which was shortly to set in. 



Milboen Wick. — This is a roadside exposure, one and three quarter miles 

 north-north-east of Frogden Quarry, where a peculiar phase of the Humphriesianus- 

 zone presents itself. About nine feet of rock is exposed, of which the lower three 

 feet are simply calciferous grits (Dew-beds). The " fossil-bed " is about eighteen 

 inches thick, and consists for the most part of a softish white limestone, not unlike 

 the marl with green grains at Oborne. In the upper part are numerous species of 

 Sphceroceras, whilst in the lower part Am. Humphriesianus and Am. Braikenridgii are 

 not uncommon. Ter. sphmroidalis occurs in the upper part of the fossil-bed. But 

 few Gasteropoda are quoted from here. 



Development of the HuMPHEiESiA.NUS-zowe in Dorset-Somerset. — A line drawn 

 from near the town of Sherborne in a north-easterly direction to Milborn Wick 

 (Somersetshire) is about three miles in length, and this line coincides with the 

 principal development of these beds in No. 1 District, a development by far the 

 most important in England, though the zone is very well represented at Dundry. 

 Henceforth, as we pass northwards into Somersetshire, the character of No. 1 

 District undergoes considerable modification. 



Coeton Down Quaeet. — Between three and four miles due north of Sherborne. 

 The Lower Division is again well represented here, since many specimens of 

 Am. Murchisona are quoted. No traces of the Humphriesianus -zone were observed 

 by me. 



Beyond this the exposures are lacking in interest from our point of view until 

 we arrive in the neighbourhood of Castle Caey. To the south-east, east, and 

 north-east of this town are three exposures in the Inferior Oolite, which have 

 yielded a fair number of Gasteropoda. As this is a district but little known, the 

 following particulars may be interesting. 



