W. T. Aveline — JLagnesian Limestone § New Red of Notts. 155 
a. margin of Talve ; b. shell exhibiting prismatic structure ; c. c. pallial 
cseca penetrating ditto ; d. great pallial sinus ; e. marginal vessels ; /. outer 
lamina of mantle ; g. external reticulated layer of ditto, in wliicli the pallial 
c*ca take their origin ; h. homogeneous layer of other lamina ; i. inner 
lamina of mantle ; j. epithelium ; k. k. merabrane lining pallial sinus ; 
tu inner ditto ; o. marginal fold ; p. one of the setae ; g. follicle of ditto ; 
r. Prolongation of glandular matter of follicle ; s. marginal muscles ; 
t. extreme pallial margin. 
( Plates IX. and X. will appear in our next Number.) 
II. — The Magnesian Limestone and New Red Sandstone in the 
Neighbodehood of Nottingham. 
By W. T. Avelixk, F.G.S., 
Of the Geological Survey of England and 'Wales. 
S INCE the Government Geological Survey of the country aronnd 
Nottingham was made in the year 1859, and the Explanation 
on the Geological Map Quarter-sheet 71 N.E. was written in 1861, 
papers hy local geologists have been written, stating that in the 
neighbourhood of Nottingham a perfect conformity existed between 
the Magnesian Limestone and the New Red Sandstone. This being 
totally at variance with conclusions I came to when I surveyed that 
country, I have been for some time past desirous to say a word on 
the subject, but being deeply occupied with the old rocks of the Lake 
district, I have put it off froin time to time. I feit little doubt in my 
mind, when surveying the neighbourhood of Nottingham, that there 
was a considerable break between the Magnesian Limestone and the 
New Red Sandstone, and this opinion was completely confirmed as 
I continued my survey northwards through Nottinghamshire into 
Yorkshire. Unfortunately I did not make a Statement regarding 
this break between the two formations in my Explanation on Sheet 
71 N.E. Wishing to compress my observations as much as possible 
to form a pamphlet, the price of which would not be more tlian six- 
pence, much that might have been of interest was left out. But in 
my Explanation on Geological Map Sheet 82 N.E., the country 
in the neighbourhood of Worksop, I have given my proofs of this 
great break. I have shown that in the district to the north of 
Worksop the Permian series consists of at least four divisions. To 
begin at the top, there are the Upper Marls ; next below the Upper 
Magnesian Limestone so-called, though it contains little or no Car- 
bonate of Magnesia ; then the Middle Marls and Sandstones ; and, 
lastly, the lowest and chief member of the Permian series, the Lower 
Magnesian Limestone. I state that the Bunter Sandstone overlaps 
the Upper Permian Marls throughout most part of the district, and 
before the neighbourhood of Worksop is reached the Upper Limestone 
is also overlapped. From Worksop southward to Nottingham there 
are only left the Middle Marls and Lower Magnesian Limestone. 
Between these two places the Middle Marls are frequently over- 
lapped, and, finally, west of Nottingham, the Lower Magnesian 
Limestone is itself overlapped, the New Red Sandstone resting on 
the Coal-measures. Therefore, in the neighbourhood of Nottingham, 
instead of there being a perfect conformity between the Magnesian 
