2 BRITISH SILURIAN BRACHIOPODA. 
described or illustrated ; and indeed it is chiefly in James Sowerby’s ‘ Mineral Conchology 
of Great Britain’ for the years 1813, 1822, and 1823, and in a paper by the same author, 
published in ‘ The Transactions of the Linnean Society’ for 1815, that some seven Silurian 
forms of Brachiopoda were for the first time correctly illustrated.* 
During several years prior to 1839, Professor Sedgwick and Sir R. Murchison had 
devoted much time and labour to the study of the Lower Palzozoic rocks, the one in 
North Wales, the other in the English and Welsh counties once occupied by the ancient 
Silures.? From these districts Sir R. Murchison had obtained an immense assemblage of 
fossils, which, with the exception of the Trilobites, described by himself, he wisely placed 
for description in the hands of the most competent paleontologists in England. These 
fossils were consequently stratigraphically arranged, described, and illustrated on the prin- 
ciple laid down by W. Smith, in his memorable work, ‘Strata identified by Organic Remains.’ 
The Brachiopoda, which are the only fossils we require here to refer to, were therefore en- 
trusted to Mr. J. deC. Sowerby, who was not only enabled to identify a certain number of 
our British Silurian forms with those already described by Continental authors, but also 
made us acquainted with a large number of other species which had not been described 
up to that period. As part of the results of this examination, we may mention the pub- 
lication of a “Stratigraphical List” in the ‘Sil. Syst.,’ as well as short descriptions and 
excellent figures of about one hundred species of Brachiopoda, distributed in the various 
geological groups or divisions established and described in the same work by Sir 
R. Murchison; and indeed, so great was the renown and success of the ‘Silurian 
System,’ that its classification was adopted not only in Great Britain, but upon the Con- 
tinent and in America. It also stimulated further researches in the same direction in 
various parts of the world ; so that the Lower Paleozoic rocks and fossils, which prior to 
1839 were so imperfectly understood, are now as well known as any of those belonging 
to the other and higher sedimentary deposits, forming part of the earth’s crust. 
We will first of all therefore very briefly allude to the most important works in 
connection with British Silurian Brachiopoda that have appeared subsequently to the 
publication of ‘The Silurian System.’ 
In 1843 a few Irish species were figured and described by General Portlock, in his 
1 Terebratula obtusa, Sow. = Meristella tumida, Dal. sp. 
— sinuata, Sow. = Orthis biloba, Linn. sp. 
_ Wilsoni, Sow. = Rhynchonella Wilsoni, Sow. sp. 
—_ afinis, Sow. = Atrypa reticularis, Linn. sp. 
Productus depressus, Sow. = Strophomena depressa, Sow. sp. 
Pentamerus Knightii, Sow. 
= Aylesfordii, Sow. 
— levis, Sow.= Pentamerus oblongus, Sow. 
‘ = The same. 
2 The reader will find in the ‘ Proceedings’ and ‘ Journal of the Geol. Society’ many important memoirs 
by Sir R. Murchison, the Rev. A. Sedgwick, and others, on the structure and arrangement of the 
Lower Paleozoic rocks. 
