THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
255 
from the fossil contents of the upper beds, I think there 
was a shallowing of the seas taking place in this district 
from actual elevation of the sea-bed. The sandy nature of 
the beds, the large amount of iron often found in the rock- 
bed, and the common occurrence of wood in the same, may, 
I think, be taken as indications of nearer, and, therefore, 
recently formed land. This gradual elevation continued 
probably till some part of the rock-bed protruded from the 
water, and suffered the erosion which it exhibits in a few 
places; other portions meanwhile remained still under 
water, and received the shallow water deposits which we have 
called the Transition Bed. 
Professor Judd (“ Geology of Rutland,” p. 65) observes 
that “ When the junction of the Upper Lias with the 
Marlstone Rock-bed is seen, the latter often presents the 
appearance of having suffered erosion before the deposition 
of the latterand also “ Taking into account all the 
characters presented by the Marlstone Rock-bed, and 
remembering the evidence of shallow water conditions which 
the beds immediately lying upon it exhibit, it seems probable 
that an interval occurred between the deposition of the 
Marlstone and the Upper Lias ; but when we remember the 
fact of the passage of certain species from one to the other, 
especially of' the Planulate Ammonites, it is clear this interval 
was not one of long duration.” 
Mr. E. A. Walford, E.G.S. (“ On some Middle and Upper 
Lias Beds in the neighbourhood of Banbury”) says :—“ The 
shelly band at the top of the rock-bed, at Aston-le-Wall 
in particular, is made up chiefly of broken and rolled 
Belemnites, separated valves of Rhynchonellas, and detached 
Pentacrinite joints, suggesting an interval of cessation 
in deposition of sedimentary matter prior to the formation of 
the next layer. One fragment I have of the rock-bed shows 
an eroded surface in the hollows of which are numbers of 
valves of Astarte striato-sulcata (Romer), for the most part in 
an upright position, and so packed as to suggest the necessity 
of a strong current to place them so. The Transition Bed 
generally at Aston presents evidences of littoral conditions 
in the worn and fragmentary character of many of the shells.” 
It is probable that the shallow sea in which the Transition 
Bed was deposited was not entirely cut off from the deeper sea 
in which the Upper Lias was developing, because distinctly 
Upper Lias fossils are found mixed with Middle Lias ones in 
this bed, though there is a great preponderance of the latter. 
( To be continued.) 
