HISTORY OF RESEARCH. clxxi 



The third division deals with the Zonal Range of all the forms of the British 

 Graptoloidea definitely recognised by the authors in the Descriptive sections of the 

 Monograph. These forms are named as amounting to 372 in number, and are 

 grouped in the order of the consecutive families and genera described in the body 

 of the work. Some thirty-six British Graptolite zones are recognised and named 

 by the authors A first table (Table A, pp. 516-525) entitled "The Zonal 

 Distribution of the British Graptoloidea," shows the presence, so far as known, 

 of each species and variety in the several British zones recognised. A second 

 table (Table B, p. 526) entitled " The Vertical Range of the Zones of British 

 Graptoloidea," exhibits the approximate relative position of each of the Grap- 

 tolite zones named in the ascending Succession of the British Lower Palaeozoic 

 formations and sub-formations generally. 



