IV 
INTRODUCTION. 
several names have been used, which of them ought to be 
preferred. In all such cases, if it is possible to understand 
by any means what was intended by the most ancient author, 
his name has been used, on the universal principle of treating 
each Naturalist as we ourselves would wish to be treated if 
we were in his position. As every original observer will con- 
stantly make use of characters which others may have over- 
looked, or not thought of so much importance as further 
research has shown to belong to them ; so when a generic 
name is used, it will of necessity be often employed in a 
different sense, or with a more restricted, or very rarely a 
more extended, meaning than its original proposer applied 
to it : if this were not allowed, many names must be added 
to the list of genera, which is, as this work proves, already 
so overburdened with synonyma. 
At the end of each species, after the general habitat, is 
added an enumeration stating the state, age and habitat, 
and other peculiarities of the specimens of the kind in the 
Museum Collection. 
JOHN EDWARD GRAY. 
