567 
[Scudder. 
TABLE Iir. TABLE OP FOSSIL HOMOPTERA PROM ROCK DEPOSITS. 
FAMILIES. 
AMERICA. 
EUROPE. 
GENERA. 
SPECIES. 
GENERA. 
SPECIES. 
Coccidae 
1 
1 
0 
0 
Aphides 
15 
32 
3 
8 
Psyllidae 
2 \ 
2 
0 
0 
Fulgorina 
16 
29 
3 
3 
Jassides 
11 
21 
8 
18 
Cercopidae 
10 
27 
4 
21 
Stridulantia 
0 
0 
1 
6 
Totals. 
55 
112 
19 
56 
This table shows clearly how poorly the Aphides and Fulgorina 
are preserved in the European as compared with the American 
rocks. 
It has been necessary to establish a large number of new ge- 
neric groups to contain the American forms, which perhaps would 
not have been the case to the same extent had a really good selec- 
tion of existing tropical American types been accessible ; for the 
affinities of nearly the whole homopterous fauna of our tertiaries 
are plainly subtropical. It is curious to see how highly developed 
some apparently extinct types were in that day ; the family groups 
were quite as trenchant as now, and while we find in some, as in 
Aphides, marked departures from modern structure, it in no way 
appears to affect the family characters or to mark any approach 
toward the neighboring groups. Some genera now apparently ex- 
tinct seem to have attained a high degree of differentiation, as 
witness Aphidopsis among the Aphides, Diaplegma among the Ful- 
gorina, Palecphora, Lithecphora and Palaphrodes among the Cer- 
copidse ; of all of these there were several species, and more than 
occur in any other generic group excepting Agallia among the Jas- 
sides, which is equal to the least prolific. As a general rule, it is also 
in just these genera that the individuals are the most abundant, nota- 
bly among the Cercopidse, which as a family is almost twice as nu- 
merous as all the others together, though among these larger families 
the least well provided with generic distinctions ; for the three 
