36 MUSEUM OF COMPARATIVE ZOOLOGY.  [Feb. 
has prepared the way for another process, which has been carried 
on to a considerable extent in a number of large groups; viz., 
that of bringing together all the species, and arranging them in 
distinct generic circles ; that is, in circles of species determined 
by generic affinities, or according to their kinds; all this being 
done in the light derived from the study of the fossils them- 
selves. And this has suggested, and if the truth of nature be 
carried out, it necessitates an additional step equally important 
with the preceding; to wit, the disposing of these several genera 
in more comprehensive groups, holding intimate or remote rela- 
tions to each other, according to their sub-family or family like- 
nesses and differences. Still another step contemplated and all 
along kept in mind, but in respect to which I have as yet done 
little in the practical arranging of the collections I am investi- 
gating, is such a co-ordination of these several large groups, as 
shall cause them to stand in due and proper relation to each 
other, as making up the various great divisions composing the 
class to which they respectively belong. j 
In connection with, yet in addition to, this work on the speci- 
mens themselves, there has been a large amount of labor 
expended in the examination and comparison, as well of the 
earlier names, figures and descriptions of species, as of those 
now prevalent, and for the most part to be met with in recent 
publications. This is necessary, in order that what has been 
heretofore done by paleontologists may be definitely known, 
and so the way made clear for intelligent advancement. It is 
also desirable, in order that every species which has been accu- 
rately named and figured, may be determined and designated 
with strict historic fidelity ; and that thus such specific groups 
as have not yet been properly worked up, may be in due time 
accurately arranged, named and described, as truth and the 
exigencies of each case shall dictate. In this direction a large 
amount of preliminary work has been done, and the result 
briefly noted, — a work which has necessitated the ransacking 
of many musty tomes, some of them long out of print, in Eng- 
lish, French, German and Italian ; for original documents have 
been in all cases consulted, so far as adit in connection 
with more recent authorities. 
There is another important aim involved in the work under 
consideration, — an aim, which as suggested by the Director of 
