British Association Reports. 519 
trary, and that there is not any physical or organic break which 
justifies the separation of the ‘ Middle’ from the ‘Lower’ Lias, as 
two distinct formations. 
The Lower Lias is divisible into a series of Limestones alternating 
with Marls, in the locality under consideration, about 80 feet in 
thickness, and a mass of Marls, in which the calcareous element is 
but slight, about 220 feet in thickness, making the total thickness 
of the Lower Lias, near Lyme Regis, about 300 feet. The litholo- 
gical passage from the lower division to the upper is however gra- 
dual, and there is not any definite paleontological break between 
them. 
The ‘Limestones’ (the ‘Blue Lias Stone’ of commerce) are the 
best known portion of the Lias. Their origin, as well as that of the 
nodules of limestone that occur in the marls above, are alike attri- 
butable to segregation from an originally calcareous ooze, and not to 
an alternate deposition of calcareous and argillaceous sediments. 
The author next considers the distribution of the fossils of the Lower 
Lias in this neighbourhood, and his observations may be summed 
up as follows: that though the Ammonites of the Lower Lias have 
very restricted vertical ranges, and do occur in the order indicated 
by the supporters of ‘Ammonitic Zones of Life,’ yet that these 
ranges do not (except in special instances, where they are limited 
by a ‘break’ in time) define the range of any associated fauna. 
That Gasteropods are generally absent in these strata, their remains 
being mostly found confined to the lowest portions of the Limestones. 
That species of Mollusca, &c., occurring in the lower portion of the 
Limestones, recur here and there again, even as high as in the 
‘Marlstone’ at the top of the Middle Lias. That the remains of 
the animal of the Belemnite are found in strata below any contain- 
ing the ‘guards’ of the same genus; the Belemnites, commonly 
so-called, gradually increasing in frequency of occurrence from the 
appearance of the Limestones to the Belemnite-beds of the Middle 
Lias. That the Reptiles and Fish of the Lower Lias appear to 
have ranged vertically throughout it, as there is no species found 
commonly which the author could assert to be confined to any parti- 
cular bed or zone; some species even passing into the basement beds 
of the Middle Lias. 
From a consideration of these paleontological facts, and of the 
lithological conditions of the Lower and the Middle Lias, the author 
expresses his opinion that these so-called formations are but sub- 
divisions of one formation representing the complementary deposits — 
of one sea. 
VII. Own THe Retative Extent or ATMOSPHERIC AND Ocranic DEnuDATION 
WITH A PARTICULAR REFERENCE TO CERTAIN Rocks AND VALLEYS IN YORK- 
SHIRE AND DeRBysHIRE. By D. Macxrytosu, F.G.S. 
(HE paper contained a modified re-statement of what had already 
appeared in the April and July numbers of this Magazine. 
[See article on the Brimham Rocks, and Surface-Geology of the 
Lake District.|| The author brought forward a number of very 
