PREFACE. 
Y a ‘type’ is meant the original specimen to which any 
generic or specific name was first assigned. Subsequent 
observers in examining specimens which agree in general 
characters with an already described form, often notice differ- 
ences which may indicate a new species, may be only due to 
incomplete description, or to the imperfect state of preservation 
of the type. In order to determine these points, it is necessary 
for them to see the actual fossil, which the author of the species 
had before him, when he wrote his description. 
The importance of preserving and distinctly marking figured 
and described specimens, has only of late years been generally 
realised. A committee of the British Association reported 
upon the subject last year’. In the Woodwardian Museum 
such specimens have been mounted on tablets of a special 
colour,—at first pink was used, but now blue, a more stable 
colour is being substituted. The plan of exhibiting all the 
types by themselves, on the top of the cabinets was tried, and, 
except where they are mounted on coloured tablets, this method 
can be recommended, as in every museum of importance, 
inferior specimens are continually being replaced by better 
ones, and thus the type, which is sometimes a poor specimen 
may perhaps get lost sight of. As soon however as the types 
1 Rep. Brit. Assoc. (Leeds), 1890, p. 339. 
