Scudder.] 
574 
[April 2, 
accordingly in what follows I have omitted all consideration of this, 
to make the comparisons more equable. For the same reason, in 
order to use the last work at all, I have instituted comparisons 
only between the families there elaborated, and have used the 
family groups in the same sense as there, except only that I have 
regarded the Pyrrhocoridse as a group of Lygeeidse. 
These four families are indeed the very ones and, as will be 
seen, the only ones which assume any importance in the American 
tertiaries, and a comparison of their interrelation as to number 
can be shown succinctly by the following table which exhibits the 
relative percentage of representation of each of these families in 
the different regions and times as represented in the published lists, 
the only available ones, and which may be supposed to represent, 
not the numbers but the relations, with tolerable accuracy. 
TABLE VI. RELATIVE VALUE OF CERTAIN HETEROPTERA IN 
SPECIFIED DISTRICTS. 
FAMILIES. 
AMER. 
TERTIARY. 
UHLER, 
WEST. LIST. 
UHLEK« 
GEN. LIST 
DISTANT, 
CENTR. AMER. 
Capsidae 
9.6 
11 
25 
27.3 
Lygaeidae 
37.8 
31.4 
19.2 
17.7 
Coreidae 
25.1 
23.1 
21.6 
21.7 
Pentatomidae 
27.4 
34.5 
34.1 
33,2 
Totals. 
99.9 
100. 
99.9 
99.9 
The correspondence of the numbers in the last two columns is 
even less remarkable than the disturbance of the relative percen- 
tages of the Capsidse and Lygseidse of the western list when com- 
pared with those of the American and Central American forms ; 
the merest indication of such an overturn is shown in the compari- 
son of the nearer American and the more distant Central American 
lists ; but the overturn is still more complete and in the same 
direction when we compare the existing and the fossil faunas of 
the west. The relative representation, then, of the four principal 
families of the tertiary Heteroptera of the western half of our con- 
tinent agrees conspicuously better with the relative representation 
of the existing fauna of the same geographical region, than with 
that of other regions of the same world. Either the physical con- 
