66 FLORIDA GEOLOGICAL SURVEY-NINTH ANNUAL REPORT. 
nized. Of mammals there are 24 species, of which 12, just one- 
half, are regarded as no longer living. It is especially the mammals 
which figure in Pleistocene faunal lists; and they are more properly 
the ones to be used in making comparison with discoveries made 
elsewhere. 
On page 26 of volume XXIII of the Iowa Geological Survey, 
the writer has presented a list of the species of mammals which 
have been found in the Aftonian interglacial deposits. These are 
21 in number, of which 19 are extinct, close to 90 per cent. It 
must be noted, however, that most of the Aftonian deposits consist 
of coarse materials and that the small species, mostly rodents, have 
not been collected. The discovery of these would quite certainly 
reduce the percentage. 
In the Iowa Report on the page noted above there is a list, taken 
from Matthew, of mammals which had been found at Grayson, near 
Hay Springs, Nebraska. These are supposed to be of the same 
geological age as those from the Aftonian. They are 21 in number, 
of which 15 appear to be extinct, about 71 per cent. 
The cave at Port Kennedy, Pennsylvania, has furnished 47 iden¬ 
tified mammals, of which 80 per cent, are extinct. The deposits of 
this cave belong certainly to the early Pleistocene. As the condi¬ 
tions there were favorable for the preservation of all kinds of land 
animals, it would seem that the normal percentage of extinct mam¬ 
mals for the early Pleistocene is about 80. What is found in any 
particular locality will depend, however, on special conditions. In 
No. 2 at Vero, there appears to be 70 per cent, of extinct mammals. 
In the Conard fissure, in Arkansas, Barnum Brown found about 
50 identifiable species of mammals, of which about 47 per cent, are 
extinct. The list is to be found on pages 31 and 32 of the. Iowa vol¬ 
ume cited above. Inasmuch as great numbers of the smaller ani¬ 
mals, especially insectivores and rodents, had accumulated there, and 
few of the large animals which it is certain were living then in that 
region, as elephants, mastodons, ground sloths, and bisons, it is not 
improbable that the percentage of extinct species is too low. On 
account of the presence of some species there which appear to be 
of a boreal type, the writer has supposed that the animal lived dur¬ 
ing one of the glacial stages, probably the Illinoisian. 
On account of the comparatively low percentage ( 5 °) of the 
extinct mammals belonging to No. 3 at Vero, the writer has been 
inclined to the opinion that the stratum belongs to the middle Pleis- 
