ON TlIK FOSSILIl-EUDUS TILiNSITION BED I.N ^•0RTHAM1'T0NSHIBE. 349 



called locally, is very variable in character, but almost always fissile. 

 The description of this bed at Bugbrook gives a fair idea of the bed over 

 the area embraced by this report. At Bugbrook it is very fossiliferous, 

 Amvi07iites communis, A. Holandrei, and A. hifrons largely predominatino-. 

 Singularly, in this bed the fossils seem to lie anyhow; many of the 

 specimens, particularly A. hifrons, stand quite upright in it, instead of 

 lying ou their sides as is usual. 



The most charactei-istic fossils of this sub-zone, besides those men- 

 tioned above, are Belemnites snbtenuis, and other long, slender forms ; 

 Trochus duplicatus, T. Northatiiptonensis, Eucijdas acuminatus, d'Orb., 

 Nucula claviformis, and Ammonites subcarinatus. 



Conclusions. 



Maps. — It may be noted here that over most of the area embraced by 

 these investigations there is a capping of Upper Lias, varying from a 

 couple of feet to 10 or 12 feet, where the maps show only Marlstone. 



The hard beds near the base of the Upper Lias seem to have protected 

 the intervening clay beds from denudation, and these latter have largely 

 protected the Marlstone rock bed itself, making it thus a more valuable 

 stone than it would otherwise have been. 



Horizon of Fossils. — The fact noted above may account for the 

 incorrect determination of the horizon of a number of fossils collected 

 many years ago by Miss Baker, now in the British Museum and other 

 places. We would particularly call attention to the specimen of Lepidotus 

 (jigas, Agassiz, now in the British Museum, which is, or was, labelled as 

 from the Marlstone of Bugbrook. This certainly came from the Fish 

 bed of that district, as did also another specimen now in the Northampton 

 Museum. 



Of the other fossils, chiefly ammonites, labelled as from the Marlstone, 

 there can be little doubt that they came from the inconstant hard bed 

 just above the Paper Shales. It seems highly probable that all the beds 

 from this Cephalopoda bed to the base of the rock bed, which constitute 

 almost one continuous hard layer, were formerly regarded as Marlstone. 



Correlation of the Beds. 



Boch Bed. — There is probably no zone of the Lias more distinctly 

 marked, lithologically and palajontologically, than the Marlstone rock 

 bed. Right across the country from Dorsetshire to Yorkshire it is 

 scarcely ever absent, and it varies comparatively little. 



The correlation of the beds above the rock bed is not quite so certain, 

 but we would submit some evidences of the contemporaneity of the beds 

 variously designated as below : — 



Bleurotomaria Bed of DorsefsMre (Day).' 

 Leptiena Beds of Somersetshire and OloncestersJdre (Moore), 

 Transition Beds of Northamptonshire (Walford). 

 Annulattis Zone ofTorlshire (Tate and Blake). 



1. The situation of each of these beds is the same, viz., just above 

 the rock bed of the Middle Lias and below the Fish bed of the Upper 

 Lias. 



' Dr. Wright did not admit that the Pleurotomaria bed of Mr. Day was the 

 equivalent of the Transition bed of the Midlands.— E. W. 



