1890 .] 
565 
[Scudder. 
often including numerous species. This is partly to be accounted 
for by a very striking feature, of which details will be given later, 
viz., the occurrence of peculiar characteristics running through all 
or nearly all the genera of entire families and distinguishing them 
from living types. Germar observed something akin to this when 
he remarked of the amber (oligocene) Hemiptera that many spe- 
cies had a relatively long beak. 
5. Existing genera which are represented in the American ter- 
tiaries are mostly American, not infrequently subtropical or tropical 
American, and where found also in the Old World are mostly those 
which are common to the north temperate zone. A warmer cli- 
mate than at present is distinctly indicated. 
6. There are no extinct families. 
7. The appearance of the same families and even of the same 
groups of genera in the European and American tertiaries is com- 
mon, but of the same restricted genus very rare. It is more com- 
mon when the American species are compared with the oligocene 
species of Europe than when the comparison is made with the Eu- 
ropean tertiary species at large. 
With these preliminary statements we may pass to a separate 
consideration of the two great divisions of Hemiptera : the Homop- 
tera and the Heteroptera. 
The variety of forms referable to the families of Homoptera, that 
have been found in the American rocks, is not a little surprising, 
and it includes some remarkable forms. All the families are rep- 
resented excepting the Stridulantia, and this exception is the more 
noticeable because the presence of this family has been signalized 
in several instances in the European tertiary rocks, and species 
believed to belong here have even been found in mesozoic de- 
posits. Yet two families, Coccidae and Psyllidae, occur with us 
and have not yet been found in European rocks, though Coccidae 
are known from the Baltic amber. In all we find represented six 
families, thirteen subfamilies, fifty-five genera, and one hundred 
and twelve species in the four hundred specimens that have been 
examined. 
The families Coccidae and Psyllidae, however, are very feebly 
represented by a few examples only. The great bulk of fossil Ho- 
moptera, both in Europe and America, belonging to the four fam- 
ilies Aphides, Fulgorina, Jassides and Cercopidae ; in each of these, 
