174
A TREATISE ON GEOLOGY.
CHAP. VI.
existing (e. g. nucula, lingula, isocardia); but others
are quite different, (as pleurorhynchus, producta, euomphalus,
goniatites, &c.), and seem to belong to another
order of creation. About 60 per cent, of the species
belong to extinct genera; and it is very remarkable,
that brachiopodous bivalves, which, in existing nature,
are perhaps to other shells as 10 in 1000, were in these
ancient periods as 10 in 34. The goniatites are most
beautiful and characteristic features of this system,
being found in none of the more recent strata.
Crustacea existed during the accumulation of these
rocks, but bore little resemblance to the present forms
of the class: the trilobites of these rocks are, however,
less numerous and varied than in the older Silurian
rocks, where they are remarkably plentiful.
Annelida have left many as yet undescribed remains
on the surfaces of the flagstones in the millstone grit
and limestone series. Some are enough like Nereis to
be referred to the wandering setigerous tribes.
The fishes of the carboniferous system (Burdiehouse,
Leeds, Bradford, Manchester, Bristol, Wales,
EXPLANATION OF FIGURES, p. 175.
1. Producta scabriculus. Sowerby. It occurs in mountain limestone generally, and in coal strata at Coalbrook Dale.
2. Producta punctata. Sowerby. Common in the carboniferous limestone.
3. Terebratula pleurodon. Phillips. Common in the carboniferous limestone.
4. Spirifera cuspidata. Sowerby. Not rare in the carboniferous limestone.
5. Pleurorhynchus minax. Phillips. From the carboniferous limestone of Ireland, Yorkshire, Derbyshire.
6. Posiclonia vetusta. Sowerby. From the limestones and shales of the north of England, the north of Ireland, &c.
7. Goniatites sphericus. Sowerby. A common shell in the limestone.
8. Bellerophon tangential is. Phillips. From the limestone of Ireland, Yorkshire, &c.
9. Orthoceras cinctum. Sowerby. From the limestone of Ireland, north of England.
10. Melania constrict. Sowerby. From the limestone of Derbyshire, Yorkshire, &c.
11. Pleurotomariaflammigera. Phillips. From the limestone of Bolland.
12. Natica plicistria. Phillips. From Boland in Yorkshire, Ireland, &c.
13. Euomphalus pentagonalis. Sowerby. Common in the limestone of Ireland, north of England, &c. Its internal cavity is divided into chambers by imperforate septa, as was first noticed by Mr. W. Gilbertson of Preston.
