INTRODUCTION 







56 PALEONTOLOGY. 



'55 : 56(41} Geology and Palaeontology of Scotland. 



In addition to the significant class number, each book 

 receives a book mark which serves to distinguish it from all 

 other books belonging to the same class. This book mark 

 almost always consists of the first three letters of the 

 author's surname, or of a word selected, according to certain 

 rules, from the title. As the author's surname or the selected 

 word appears first in the clarendon type at the beginning of 

 each entry of the catalogue, the book mark has not been 

 reprinted at the side. In the case, however, of periodicals 

 and publications of societies, where the same first words 

 (Journal, Annals, etc.) recur with frequency, it is necessary 

 to choose, more or less arbitrarily, certain letters, usually 

 initials, to represent the titles. These letters are printed 

 immediately after the class number of each book. Thus : 



504 Helmholtz, A. von. Popular lectures on scientific sub- 



jects. 



'5(26) Challenger. Report on scientific results of voyage. 

 5805 A.B. Annals of botany. 

 5806 L. j. Linnean Society. Journal. 



The actual book mark of the first of these is Hel, of the 

 second Cha. 



Certain groups of books, though dealing with different 

 subjects, it has been found convenient not to disperse. These 

 are denoted by distinctive letters placed immediately before 

 the class numbers. Thus : 



B.M. = British Museum publications. 



R.s. = Royal Society's publications. 



Ref. = Reference books, bearing red labels, and not to be removed 



from the library. 



/. = folio books, placed on special shelves. 

 p. = pamphlets, placed in boxes. 



It is, of course, not expected that readers can remember 

 all the numbers corresponding to the different subjects. A 



xi 



