186 
SILUKIA. 
[Chap. IX. 
CHAPTER IX. 
ORGANIC EEMAINS OF THE LOWER SILURIAN ROCKS. 
A pull acquaintance with, the Silurian Fossils of the British Isles can be 
gained only by a study of the various works in which they have been 
successively described. Of these works, the first in which the fossils were 
classified and placed in their true geological position is the ' Silurian 
System ' * ; the next is a Report on the Silurian fossils of Tyrone, by 
Portlock ; a third, on the Silurian fossils of Ireland, by At' Coy. Then 
follow various publications of the Government Geological Survey, par- 
ticularly the volume on the Malvern and Abbeiiey Hills, by Professor 
Phillips and Mr. Salter, certain monographs descriptive of both Lower 
and Upper Silurian forms, in the Decades of the Geological Survey, by the 
late Professor E. Forbes and Mr. Salter, and the Appendix by Mr. Salter 
to Professor Ramsay's ' Geology of North Wales' (Mem. Geol. Surv. vol. 
iii.). Notices of Silurian fossils have also been published by Mr. D. 
Sharpe, Mr. Salter, and other writers in the volumes of the Quarterly 
Journal of the Geological Society of London. A detailed description of 
the Upper Silurian Brachiopods, by Mr. Davidson, appeared in the Bul- 
letin of the Geological Society of France, nearly all the British species 
being there figured and described. In the Introduction to his Monograph 
of British Fossil Brachiopods (vol. i.), Mr. Davidson has described their 
generic characters ; and his special Monograph on the Silurian Brachio- 
pods, published by the Palseontographical Society, is a work of the highest 
order of merit. Three parts of Mr. Salter's Monograph of the British Tri- 
lobites have also been published by the same Society. Professor Rupert 
Jones has described most of the small Bivalved Crustaceans of the Silurian 
rocks, in the 'Annals of Natural History.' Lastly, an important addition 
has been made to our knowledge of the British fossils of this age through 
the publication, by Professor Sedgwick, of Professor M'Coy's descriptions 
of the Palaeozoic fossils in the Woodwardian Museum of Cambridge. This 
work, to which references are often made in the present volume, contains ela- 
borate descriptions of upwards of 300 species, with figures of the new forms. 
The reader who consults these various works f will find that, whilst 
a marked division was at first particularly insisted on, by myself, as ex- 
isting between the Lower and Upper Silurian, subsequent researches, 
extended over large areas, have shown that the two groups are much more 
closely knit together in one natural series than was formerly supposed, — 
it being now well ascertained, as already explained, that a considerable 
* The Shells of the ' Silurian System' were de- t In the ' Geologist,' vol. i., I808, Prof. Morris 
scribed by James de C. Sowerby, who had pre- published a very useful List of Books and Memoirs 
viously figured and described some of the species relating to Silurian and Cambrian Geology, com- 
in bis 'Mineral Conchology.' The latter were pi etc to that date, 
chiefly from the Wenlock Limestone. 
