THE NATURE OF A SPECIES IN PALEONTOLOGY, 
AND A NEW KIND OF TYPE SPECIMEN 
EDWARD L. TROXELL 
Yale University 
In discussing the subject, ‘“What is a species ?”’ with my asso- 
clates in vertebrate paleontology, many points of interest have 
come up which will bear repeating. The great complexity of the 
problem and the number of elements which enter into its com- 
position make the solution difficult—perhaps impossible—for 
certainly no single definition can apply in every case. 
Professor Schuchert has said that he finds it best to let the man 
who is studying a given specimen decide what a species is, after 
he has read several definitions, and that even for students who are 
writing their first papers it is best left to the individual; he may 
stand or fall on his ingenuity in handling this unanswerable question. 
The more deeply we go into the study of a specimen, not only 
do the features multiply, but they increase in importance, and 
thus we raise a variety to a species, or a species to a genus. Along 
with the personal element and the extent of our knowledge, very 
important factors indeed, we must in paleontology consider another, 
viz., the actual worth of the specimen, and it is undeniable that a 
new species should not be made on fragmentary material unless its 
characters are unique and of such importance as to reveal the 
existence of a new and strange group of animals, hence scarcely 
less than a genus or even a family. As an example of such speci- 
mens, whose discovery gave us the first knowledge of strange 
groups, there may be mentioned Archaeotherium mortoni Leidy, 
Ammodon leidyanus Marsh, or Rhinoceros occidentalis Leidy. 
It is a well-known fact, and yet one not fully recognized, that 
new types based on good specimens are and should be made, to 
supplant older inadequate ones. We may cite as an example the 
mammal Dinohyus Peterson, which Matthew says is not different 
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