ON THE FOSSILIFEROUS TIUNSITION BED IN NOETIIAMrTONSUIKE. 347 



The stone, which has got coloured light-brown throughout, nearly 

 always shows a large number of parallel, nearly microscopic veins, extend- 

 ing right across the stone. The veins look like, and pi-obaby are, minute 

 cracks filled in with crystallised cai'bonate of lime, and on the weathered 

 surface of such stones these veins stand out in relief. The same character 

 was observed in the Fish bed of Alderton, Gloucestershire. 



The above is a description of the bed as it occurs at Milton, Bngbrook, 

 and some other parts of the county, but at Arbury Hill, Catesby, Byfield, 

 Chipjjing Warden, &c,, it is quite diS'erent. At these places it is very 

 irregular in composition and difficult to describe ; it weathers rather yellow 

 than white, contains fewer fish remains and more ammonites. The Paper 

 Shales have not been detected where there is an abundant ammonite fauna 

 in the Fish bed, hence the suggestion that this is an attenuated zone re- 

 presenting in time and in fossil contents more than one of the beds given 

 in the general section. Another reason may be found in the singular 

 absence of anmionites of the genus Stephanoceras from the Fish beds of 

 Milton and Bugbrook, although found above and below, and their great 

 abundance in the Fish bed of Arbury Hill and Catesby, &c. 



The most distinctive fossils found in the Fish bed, besides the fish 

 remains, arc the Aptycld of Ammonites, cephalopods allied to the Loligo 

 and Sepia, CeritJdum gradatum ? Euomj^halus minidus, Inoceramus dubiiis 

 and a Goniomya. 



H, J. The Paper Shales are finely laminated shales having a very 

 regular and clean plane of division. When exposed to a dry atmosphere 

 the thin layers often exhibit a tendency to spontaneous separation from 

 each other, and even curl up at the edges. 



The shales at any place are closely like the Fish bed at the same place 

 in colour, &c., and there is no doubt that the Fish bed proper must only 

 be regarded as a more indurated portion of tbe shales. This easily 

 accounts for more than one hard layer at some places (cf. Milton). 



So far as we can judge, the fossils in the shales and Fish bed are 

 identically the same, only that in the shales the ammonites are mostly 

 crushed quite flat. The crushing may perhaps be accounted for by an 

 abundance of organic matter in those beds, which, as it decayed, per- 

 mitted them to give way under the pressure of sediment above. Ammo- 

 nites e^ratus seems to have resisted compression better than the other 

 ammonites. 



The sudden appearance and decline of fish is a matter deserving of 

 attention. Not a fragment of any kind appears to have been found in 

 the Marlstone, and scarcely any in the beds just above the Fish bed. 



The shales are better developed at Milton and Bugbrook than else- 

 where in the county. 



C, D. The Serpentinus Beds. — These beds form the upper portion only 

 of what is usually called the ' Serpentinus ' zone ; the latter would include 

 the Fish bed and shales. Mr. Buckman recommends that these beds be 

 called the Falcifer beds and the zone the Falciferum zone, because, 

 although many ammonites of the falcifer group occur, very few agree with 

 the type of A. serpentinus itself ; hence a more general term is desirable. 

 This would agree with the Continental nomenclature. 



This sub-zone rests upon the Fish beds, and usually consists of a bed of 

 calcareous clay, capped by an argillaceous limestone containing some large 

 ammonites of the ' Falcifer ' group. 



K, F. — This investigation has brought out the fact that there is a 



