GEOLOGICAL DISTRIBUTION. 97 
The only examples of the Calcispongie yet discovered in our area are minute 
detached spicules in the Carboniferous Rocks of Fifeshire. 
GroLocicAL Disrrisurion. 
Cambrian System.—The lowest rocks in which fossil Sponges have been met 
with are hard, black, slaty beds, belonging to the Menevian series near St. 
David’s, South Wales. The examples of Protospongia occurring in them, have their 
spicules replaced by iron-pyrites or iron-peroxide. The same genus is present in 
nearly similar rocks at Krekling and other places in Norway, associated with 
Paradowides. 
In hard, slaty rock of the Tremadoc series, near St. David’s, the earliest known 
example of Hyalostelia was discovered by Dr. Hicks, F.R.S. 
Ordovician System.—In the Llandeilo district of North Wales, at Tre Gil, 
South of Llandeilo, Pont Ladies, and near Shelve, in Shropshire, the anchoring 
spicules of Hyalostelia are of not unfrequent occurrence in the hard, dark, 
calcareous shales of the Llandeilo series. The same genus is present in a dark 
slaty rock at Dobb’s Linn, Moffat, Dumfriesshire, as well as in light grey limestones 
of Ordovician age, in the Girvan area of Ayrshire; and from the same rocks 
Professor H. A. Nicholson has obtained Hindia jibrosa, Roemer. In a slaty rock 
of Lower-Llandeilo age at Garn, Arenig, Wales, /schadites makes its first appear- 
ance. The Caradoc shale of Haverfordwest, South Wales, has yielded a single 
pyritized example of Astylospongia. 
Silurian System.—Alike in the calcareous shales of the Wenlock and Ludlow 
series, the genus Ischadites is widely distributed. At Woolhope, in the Dudley 
and Malvern areas, Usk, near Buildwas, Shropshire, examples have been met 
with. 
In the Dudley and Malvern areas, spicules of Astr@ospongia are sparsely present, 
and near the ‘‘ Craven Arms,” Shropshire, Hyalostelia and Atractosella are found 
in decayed limestones. 
A well-marked horizon for fossil Sponges occurs in the Pentland Hills, near 
Edinburgh. The rock is a decayed limestone of Upper-Ludlow age. Itis charac- 
terised by Amphispongia ; examples of Plectoderma and Ischadites also are present 
in it. At Mocktree, Shropshire, a sandy rock of Aymestry age is characterised by 
Phormosella ; and the only British examples of Dictyophyton have been met with 
in arenaceous beds of Upper-Ludlow age, near Kendal, Westmoreland. 
Devonian System.—In the limestones of the typical area of this system, at 
Newton Bushell, Devonshire, Sphwrospongia occurs; at the adjacent Newton Abbot 
detached spicules of Astr@ospongia are present in decayed limestones, and at Mud- 
