14 
INTRODUCTORY REMARKS. 
Various difficulties also attended the preservation of the skins when col- 
lected; and we have to regret that, from the length of time which elapsed 
before they reached England, so much injury has in many instances accrued 
to the specimens as to prevent an accurate decision respecting their characters. 
The number of species described, which is strictly limited to such as from 
their good condition afford distinctive characters, will consequently be no 
adequate criterion of the extent of the subjects actually collected, or of the 
active exertions of the collectors. 
The most important part of the following observations is that supplied by the 
officers of the expedition from their notes on the comparative anatomy of many 
of the species. Information of this nature is so valuable, and so seldom afforded 
to the home naturalist, who rarely has more than the superficies of a subject 
to work upon, that we cannot sufficiently praise the practice in this respect of 
our present voyagers, or hold it out with sufficient earnestness as an example 
to others similarly circumstanced. For the liberal and friendly feelings with 
which information on every subject connected with my department of the 
present undertaking has been communicated to me by every officer connected 
with the expedition, I have to express my warm acknowledgments. 
