Barber . — On the Structure of P achy theca. 145 
which passes obliquely into it, so that the connection is hidden 
in a transverse section. 
The sections upon which the foregoing account is based 
being manifestly insufficient for a definite statement as to the 
systematic position of the plant, it occurred to me, while on 
a visit to Norton in Shropshire, in June 1888, that I might 
obtain some more specimens of Packytheca from the rocks 
of the neighbourhood, which form the transition between the 
Silurian and Old Red Sandstone ; and accordingly I set to 
work to examine the Downton Sandstone, so extensively 
quarried in this district as building stone. In the study of 
these rocks I was greatly assisted by the Rev. J. D. la 
Touche, of Craven Arms, who also placed in my hands a 
specimen of rock containing Packytheca . 
The result of my examination was that, in every one of the 
half dozen quarries explored, Packytheca was found either in 
a carbonised or pyritised state ; and it was usually ac- 
companied by Lingula cornea , fragments of Crustaceans, 
small pieces of carbonised f wood, 5 and other organic remains. 
The quarries examined were those at Norton, Onibury, and 
Forge Bridge near Downton Castle. In most of these the 
rock is no longer worked, and I was dependent for my 
specimens on loose pieces of stone ; but in the fine new 
quarry in the Aldon Lane, near Onibury, I succeeded in 
finding many specimens of Packytheca in situ. And I am 
satisfied that the plant is not confined to one horizon, but 
occurs at numerous different levels, being especially abundant 
in the thin layers between the massive courses of fine stone. 
My attention was next directed to the Woolhope district, 
in which Strickland long ago detected Packytheca . I was 
only able to spend one day in this neighbourhood, but, in the 
Perton Quarry, near Stoke Edith, I found Packytheca in great 
abundance. Specimens from all these localities, together 
with a remarkably resistant one from the passage beds at 
Ledbury, were submitted to the best London lapidaries for 
cutting. In all specimens which allowed of grinding, the 
cortex turned out to be pyritised, and I was consequently 
