THE BRITISH FOSSIL BRACHIOPODA. 343 



From 1501 to 2000 fathoms 4 species. From 2001 to 2900 fathoms 3 species. 



Thus out of 107 species some 57, or about half the known species, were dredged at 

 a depth of less than 100 fathoms ; 20 to 25 at low-water mark or from 5 to 10 fathoms ; 

 and the remainder at about 50 to 60 fathoms. 



These numbers must, however, as I have already said, be considered as strictly pro- 

 visional, and as the result of our present experience ; but they are sufficient to indicate that 

 the majority of known species live at comparatively small depths ranging up to 500 

 fathoms, and that Brachiopods have hitherto proved themselves to be specifically rare 

 at depths of from 500 to 2900 fathoms. 



Fossil genera and species; and Classification. 



An accurate knowledge of the Families, Sub-families, Genera, and Species that com- 

 pose the Brachiopoda is a matter of considerable importance to the Stratigraphical Geo- 

 logist, for these fossils occur under a multitude of characteristic forms in our sedimentary 

 or fossiliferous deposits, and assist in defining geological epochs and horizons. Little, 

 however, seems to have been achieved in this direction during the years that elapsed 

 between 1606 and 1700 in addition to the short notices of Colonna in 1606 and 1616; 

 Worms in 1655, Lister in 1688, 1 Llwyd in 1699, 2 and a few others. The last two 

 named authors being the first, as far as I am aware, who published brief notices and 

 figures of a few of our British species, and which are in most cases easily recognisable. 



During the following century, or from 1700 to 1800, a much larger number of 

 naturalists described and figured fossil Brachiopoda ; but one should scarcely say described, 

 for in most cases they knew very little of the true nature of the animals they had before 

 them. 



If we cast a glance at the works of Langius 1752, Morton 1712, Klein 1753, 

 Stobaeus 1731, Bourguet 1742, Scheuchzer 1752, Andrea 1763, Knorr 1753, Davila 

 1767, Retzius 1781, Hupsch 1781, Faujas de St. Fond 1799, Walcott, 1799, and of 

 others whose names and works will be found recorded in the Brachiopod Bibliography, 

 we shall appreciate the immense amount of real and accurate work afterwards achieved, 

 during the years between 1800 and 1884. The rules of nomenclature laid down by the 

 immortal Linnaeus in 1753 — 1767, having been adopted by the British Association and 

 by the scientific men of every country, proved a very great boon to science. 3 



1 ' Historia sive Synopsis methodica Conchyliorum,' Appendix to vol. iii, 1C88. 



2 ' Lithophylacii Britannici Ichnographia,' 1699, 2nd ed., 1/60. 



3 Linne's types are in the possession of the Linnsean Society of London, and have been carefully 

 studied by J. W. Salter, D. Sharpe, S. Hanley, and myself (see Hauley's ' Ipsa Linnsei Conchylia,' 

 London, 18.55. Linne kept his specimens in small square tin boxes, and sometimes examples belonging to 

 more than one species had got mixed together. Since they came into the possession of the Linnsean 

 Society they have been mounted upon tablets, and, as far as such was possible, correctly identified and 



