THE ZONAL KANGE OF THE BRITISH 



GEAPTOLOIDEA. 



In the preface to this Monograph it was pointed out (Preface, p. 4) that "the 

 primary need for a work of this kind was the natural demand of the field geologist 

 and the palaeontologist for figures and descriptions of the British species." Having 

 now completed the figuring and description of the first and most typical section of 

 the British Graptolites — namely, the GrRAPTOLOIDEA — we shall best serve the 

 interests of the field geologist and the palseontologist if we here summarise in 

 tabular form the main facts bearing upon the vertical range and association in the 

 British Isles of the various species and varieties of the Graptoloidea noticed in the 

 preceding descriptive pages (pp. 1-513) of this Monograph, retaining throughout, 

 for the sake of convenience of reference, the same relative palseontological order. 



The first detailed arrangement of the British Graptoloidea (Rhabdophora of 

 Allman) in successive chronological zones was made by Lapworth in his memoir 

 " On the Geological Distribution of the Rhabdophora " ('Ann. and Mag. Nat. 

 Hist.' [5], vols, iii, iv, v and vi, 1879-1880). For the sake of brevity, that work 

 is here referred to as the Memoir and the present work as the Monogrwpli. 



The first of the Tables here presented — Table A, "The Zonal Distribution of 

 the British Graptoloidea" — maybe most simply regarded as the second and greatly 

 extended edition of a combination of Table X (showing " The Vertical Range of 

 the Genera and Species of British Rhabdophora ") and Table XI (showing " The 

 Vertical Distribution of the Tribes, Families and Genera of the Rhabdophora in 

 the Chief Graptolite Zones of the Lower Palaeozoic Rocks "), as given in the Memoir 

 above referred to, but here carefully brought up to the present standard of know- 

 ledge and opinion. 



A comparison of Table A with the tables, lists and letterpress in the Memoir 

 affords a striking index of the advance of our knowledge of the Graptoloidea 

 during the thirty-three years' interval which separates the Memoir and the present 

 stage (1913) of this Monograph. In the Memoir some 20 Graptolite zones were 

 recognised; that number has now been increased to 36. In the Memoir some 

 28-4 species and varieties of British Graptoloidea were referred to ; that number 

 has now risen to 372, in spite of the suppression of several so-called species here 

 regarded as being founded on appearances due to conditions of preservation, etc. 



