126 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



chance of any observer adding to his list without being able to devote 

 very much more time to the subject than I have had at my disposal. 

 There is certainly no formation in England, and probably none 

 abroad, the fossils of which have been the object of researches more 

 assiduous and more conscientiously made than those of Mr. Searles 

 Wood. Not only has Mr. Wood formed collections rarely equalled 

 in their completeness and extent, but he has also ably described and 

 illustrated them in the early volumes of the Palaeontographical 

 Society*. The other organic remains of the Crag have also been 

 described in the same work by most competent authorities in the 

 different natural-history sections in the following order : — 



MoUusca, by Mr. Searles Wood (PaloBontogra- 



phical Society's Monographsf) 1848, 1850. 1856 



Corals, by MM. Milne-Edwards and J. Haiine.. 1850 



Cirripedia, by Mr. Dar\^^n 1851, 1854 



Braohiopoda, by Mr. Davidson 1852 



Echinodermata, by Mr. Edward Forbes 1852 



Entomostraca, by Mr. Rupert Jones 1856 



Polyzoa (Bryozoa), by Mr. Busk 1859 



Foraminifera, by Messrs. Jones and Parker 1866 



We are thus, with the exception of the Mammalia, which are 

 only of recent discovery in the Coralline Crag, furnished with a veiy 

 complete exposition of the fauna of this formation ; but there is still 

 work to be done in defining more exactly, by careful collections on 

 the spot, the fossils of each particular zone. In zones d and / this 

 has been partly done. Zone c is typified at Eamsholt, and may be 

 characterized by its Echinoderms and various large Testacea (see 

 list), as zone e is by its profusion of Bryozoa. 



MoUusca. — So large a proportion of the shells of the Crag are 

 of recent species that we are furnished with unusually good data 

 for investigating the conditions under which this deposit was 

 formed, by the study of the geographical range and distribution 

 of those living species, and of the zones and depths through which 

 they range. The tendency of natural history at present is rather 

 to extend and remove the barriers of special zoological provinces. 

 Mr. Gwyn Jeffreys remarks % : — " It seems to me, after a long 

 and careful study of the question, that no more than two groups 

 (which are apparently distinct from each other) can be recog- 

 nized in a geographical point of view ; and for these I would sug- 

 gest the general but not inappropriate names of ' Northern ' or 

 ' North-European,' and ' Southern' or ' South -European.' " And he 

 adds that " it is extremely difiicult to fix the limits of even those 

 comparative areas of distribution ; but the ' facies ' of each group is 

 manifest to some extent in the littoral or shallow-water species," 

 To these groups, or divisions, Mr. Jeffreys adds a third, viz. 



* I am happy to hear from Mr. Wood that he is engaged upon a supplemenb 

 to his original work. 



t Last year (1870) the first part of Prof. Owen's ' Fo.ssil Cetacea of the Red 

 Crag' was added to this series. 



\ British Conchology, i. introd. p. Ixxxvi. 



