GEOLOGY AND PALEONTOLOGY. 165 
nevertheless the greater part of it has permanent value. Notwithstanding the 
fact that the fossils with which he works are extremely unsatisfactory, still there 
remains a great mass of material which is not only of extreme general interest 
but also of positive value in determining the age of the rock in which it is found 
as well as the phylogeny of the plant forms. These statements are ordinarily ac- 
cepted with more or less of reservation by investigators along other lines. 
It is possible that this undesirable condition of affairs has arisen partly from 
a misunderstanding of terms and partly on account of the methods employed by 
the paleobotanist. During the early history of this science, as of all others, 
vegetable paleontologists were too often content with simply multiplying species 
rather than in working out the phylogenetic problems of plant life. Much of the 
work will stand; while a great part of it must eventually be revised, as the work 
of the older botanists has been revised. The work along paleogenetic lines could 
scarcely have been done earlier because of insufficient data; but the time has 
arrived when, if paleobotany is to keep pace with other sciences, this vital point 
may not longer be neglected. 
The terms ‘‘species,’’ as employed by the botanist and by the paleobotanist are 
not to be considered synonyms. This fact was tersely stated by Mr. Lesquereux 
in his first paper, in 1868, as follows: ‘‘ It is well understood that when the word 
‘species’ is used in an examination of fossil plants it is not taken in its precise 
sense. For, indeed, no species can be established from leaves or mere fragments 
of leaves. But as paleontologists have to recognize these forms described and 
figured, to compare them and use them for reference, it is necessary to affix to 
them specific names, and therefore to consider them as species.”’ 
In other words, the term ‘“‘species,’’ as it has been employed by paleobotan- 
ists, is little more than a convenient handle with which to manipulate certain 
more or less identical forms. Noone who has given the matter any attention can 
be unaware that the identification of species from leaves alone is in many cases 
impossible. Leaves of a dozen species of living willows, for example, are so simi- 
lar in nervation and outline that, if mixed up, they could not afterward be re- 
ferred to their proper species by any living botanist; while, on the other hand, a 
dozen leaves taken from the same cottonwood tree might be placed in half that 
number of different species. 
The identification of fossil leaves rests chiefly upon two points: form or out- 
line, and nervation. Of these, nervation is generally considered as determin- 
ing generic, and outline specific, differences. That these points obtain for some 
plants appears reasonably demonstrated; but their universal application remains 
to be proven. The subject of the nervation of dicotyledons has never been 
worked out, save in a general way, and it is one of vital importance to the science 
of paleobotany. In view of these facts, then, it would seem that until this ques- 
tion is settled the continued indiscriminate naming of new species on slight and 
often fancied variations in form or nervation can only add to the apparent confusion 
into which the science has fallen. 
It is not deemed expedient in this connection to enter upon an extended dis- 
cussion of the genera andspeciesof thegroup. ‘‘The Flora of the Dakota Group’” 
contains practically all the forms so far recorded, and to it the reader is referred 
for details. 
INVERTEBRATES. 
The invertebrates found by Professor Mudge in Saline county, Kansas, and 
considered by Meek and Hayden as representing Dakota forms, are now gener- 
ally conceded to belong to the Comanche series. The ‘‘ Mentor beds,”’ as these 
horizons were termed by Professor Cragin, are now considered as the northern 
