CEPHALopopa. | LOWER PALAZOZOIC FOSSILS. 825 
diameter; diameter of tube at origin of straight portion four lines, width at same point three and_half lines ; 
surface marked with thin round ridges, extending obliquely outwards and backwards, increasing in strength and 
forming a round retral wave on the outer side, nearly twice their thickness apart, about four in three lines at 
three to four lines in diameter, the intervening concave spaces with three or four faint, minute, imbricating striv 
having the same direction; arched end tapering at the rate of three and half lines in one inch. 
Position and Locality.—Wenlock limestone, Ledbury, Herefordshire; Upper Ludlow of Underbarrow, 
and High Thorns, Kendal, Westmoreland. 
RESUME OF THE DISTRIBUTION OF THE LOWER PALOZOIC FOSSILS 
DESCRIBED IN THE PRECEDING PAGES. 
As much geological interest attaches just now to the distribution of the Fossils in the Lower Paleozoic 
groups of rocks, I have drawn up the following Lists, shewing the geological and geographical range of all the 
species of this age, above described, from the specimens in the Cambridge Museum. The first is a List of 
all the localities, arranged in alphabetical order, to facilitate reference ; and to each locality Professor Sedgwick 
has added his geological interpretation of the age of the rock, there occurring, from which the specimens 
were obtained. IlI-health, and press of other occupations, prevented him furnishing me fully with his views on 
these points in time for the publication of the first fasciculus of this Work (comprising the first 184 pages), 
in which I therefore thought it desirable to omit the geological position of most of the Lower Paleozoic 
localities, but the reader can now supply this information from the Alphabetical List. Another use of this first 
List, and the main one for which it was drawn up, was to enable me to save a great deal of space in the second 
List, by designating by xumbers the corresponding localities in which each fossil species is found—thus in the 
second, or systematic Fossil-list, 12 always stands for Aymestry, and 13 for Bala, &c.:; and as the numbers in 
the first List are in numerical order, as well as the corresponding localities in alphabetical order, it is easy by 
reference to ascertain either the locality denoted by any number, or the number indicating any required 
locality in the second List. 
The second List is a systematic enumeration of all the Lower Paleozoic species described in the foregoing 
part of this Work. ach species is preceded by a number indicating the page at which it is described ; under 
each specific name the localities from which Professor Sedgwick has obtained examples of the species, are 
brought together under his stratigraphical groups; and under each geological group all the localities he 
considers of that age are indicated by numbers, referring to the first, or alphabetic, List of localities. 
As it is very important, in the discussions as to the relative ages of the rocks of the various localities, to 
be able to consult a complete list of all the species from each place by itself, 1 have drawn up the third List 
on this plan, founded, like the others, on the specimens collected by Professor Sedgwick, and capable of being 
consulted in the University Collection. It takes the localities in alphabetic order, and under the head of each 
locality is given a complete list of the species occurring there, of which we possess sufficiently good specimens 
to be clearly identified. 
Professor Sedgwick has furnished the geological data of these Lists, and to him belongs the task of 
explaining the geological bearings of the rocks of all the localities from his field-books and maps; my task— 
now completed—having been, carefully to examine the whole of the collections, to determine the various species 
to the best of my ability, and to register them faithfully, wholly unbiassed by any stratigraphical considerations. 
