ON 
THE GRAPTOLITES OF COUNTY DOWN. 
By CHARLES LAPWORTH, F.G.S. 
The Graptolites discovered by Mr. Swanston in the black carbonaceous shales 
among the Silurian rocks of County Down constitute a very distinct assemblage, 
which is identical with that afforded by the Graptolitic bands forming the well- 
known Moffat Series of the south of Scotland. In Scotland the containing 
deposits have already furnished sufficient stratigraphical and palaeontological 
evidences to allow of the determination of their natural divisions and subdivi- 
sions, and of their precise systematic position in the general succession of Silu- 
rian deposits. The black shales of County Down, however, are so excessively 
convoluted and shattered, that as yet it has not been found possible to fix either 
their total thickness or the characteristics of their component zones. That the 
general grouping of the beds among them is essentially similar to, if not iden- 
tical with that of the Moffat Series, may nevertheless be regarded as certain. 
Exactly as in South Scotland, certain special forms are invariably found in 
association, while the proportion of the species, and the lithological features of 
the containing beds, are absolutely identical with those of the corresponding 
zones of the Moffat Series. It is possible that in the future, local stratigraphi- 
cal testimony respecting the inter-relations of the various beds may be detected ; 
but the sequence of the different fossil groups in the South of Scotland is so 
clear, that beyond demonstrating their identity with those of the Moffat Rocks, 
this would add but little to our present knowledge. 
The Coalpit Bay Division of the County Down Silurians has yielded all 
the Graptolites of the Birkhill shales, with the exception of one special group, viz., 
that of the Rastrites maximus zone, which lies at the very summit of the Moffat 
