ADVERTISEMENT TO SECOND FASCICULUS. v 
Under each genus, the several species are referred to their proper geological groups, agreeably 
to the scheme given in the above Tabular View. To save space the localities are, in each 
case, given by the help of numbers: but these numbers may be immediately translated into 
proper names by consulting the preceding List (commencing p. 326). For example: Vioa 
prisca—the first fossil of the Systematic List, is referred to Lower Ludlow or Wenlock 
shale. The number, 169, attached to it, gives (by help of the previous List) Malvern, Worcester- 
shire, for the locality. Here the locality is of no value, because many different formations 
are found near the Malverns: but in very many cases the locality may confirm, or, it may be, 
invalidate, the assertion of the text. Again, if we turn to the 24th genus, Stenopora, we see, 
(p. 338) that the first species (jibrosa) has a very wide range, from the Upper Ludlow to the 
Bala group inclusive: not less than twenty-nine localities are given to this species from the 
Upper Bala, or 3. of the Tabular View. The last number (122) indicates the last locality 
from which I have obtained the species: viz. the flagstone of Horton in Ribblesdale. 
This Systematic List shews that no small labour has been bestowed upon the formation 
of the collection; and also shews the enormous amount of labour bestowed upon it by 
Professor M°Coy. A bare list of species might mislead us while we are, on fossil evidence, 
endeavouring to determine our successive geological groups. <A fossil may be highly cha- 
racteristic of one group, and may be found in it in thousands; yet an individual of the 
same species may, perhaps, straggle into an upper group of which it cannot be called 
characteristic. Several cases of this kind occur in the present Systematic List; and in all 
such cases, if the geological place of the localities has not been well determined, the excep- 
tions to what seems to be a general rule almost entirely lose their value. 
When by this kind of sifting the species are, as far as possible, referred to their true 
groups and localities, there still remains this question: What is the fossil evidence offered 
by each locality? Now this evidence is put before us in a third List, which gives all the 
fossil localities alphabetically, with an enumeration of all the fossil species found under each 
head. 
By help of the three Lists above described (which have been very carefully reduced by 
Professor M°Coy) all the geological information to be at present derived from the Lower 
Paleozoic fossils of the Cambridge collection is at once given to the reader. 
That the nomenclature adopted in the Tabular View is geologically and geographically 
true, I have shewn, in a memoir before alluded to (Journal of Geol. Soc. Vol. xut. p. 136); 
and that my nomenclature of the Cambrian series has the claim of priority is certain. 
What is the scheme proposed? That the great Longmynd group, which, if seen at all, is 
very faintly represented in Wales, is to be called exclusively Cambrian; and that the grand 
Cambrian Series—not less than 25,000 or 30,000 feet in thickness—is to be called Silurian; 
although the whole map of Siluria contains only one group of that great series—the Caradoc 
sandstone—which is referred to its right place in the general section of Wales. It is true that 
the Llandeilo flagstone is described, and its fossils enumerated, in the “ Silurian System.” But 
the group was not put in its right place in the general section of Wales. Its position was 
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