436 TERTIARY INSECTS OF NORTH AMERICA. 



ten genera, and of each of these species more than a single example has 

 rarely been found. While therefore the prevalent subfamilies are the same 

 on the two continents, one has scarcely half as many representatives in 

 America as in Europe, while the other has half as many more.' 



A very striking peculiarity is found in the American Pentatomidse as 

 a whole, whether Cydnida or Pentatomida. In living forms the vast majority 

 have a long scutellum reaching beyond the middle of the abdomen, and 

 have the tip produced, forming a parallel-sided apical lobe. In the Ameri- 

 can Tertiary forms, so far as yet known, with only a single exception, no 

 such apical lobe exists, but the scutellum ends with an angular apex, some- 

 times a little rounded, but the sides perfectly straight and confluent at least 

 in the apical half; besides which, or perhaps partly as a consequence, the 

 scutellum does not reach farther than, sometimes does not attain, the middle 

 of the abdomen. It has seemed necessary therefore to establish a consid- 

 erable number of new generic groups to embrace these remarkable forms. 

 To judge from the illustrations given by Heer the same thing would seem 

 to be true of at least a few of the European Tertiary Pentatomida, espe- 

 cially of those from Hadoboj, and it would be very desirable to institute 

 direct comparisons between specimens from the two continents. 



In our general remarks in the introduction to the Heteroptera we called 

 attention to the close relation which existed between the proportional 

 abundance (in the number of specific forms) of the four principal families 

 of Heteroptera in Tertiary times, and the same in the existing fauna of the 

 self-same region. A further illustration, but even more exaggerated, appears 

 by using the same guides in comparing the relative numbers of the Cydnida 

 and Pentatomida, the only two subfamilies of Pentatomidse known to exist 

 in our Tertiary deposits and so capable of comparison. In Distant's work 

 the Cydnida number about one-sixth of the total number of Cydnida and 

 Pentatomida ; in Uhler's general list, one-seventh ; in his western list, one- 

 fourth ; the increasing number thus shown in the region where the fossils 

 occur is vastly exaggerated in their relative representation in the rocks, 

 this being two-thirds the whole. 



Subfamily CYDNIDA Stal. 



This subfamily is well represented in the European Tertiaries, and is 

 indicated as occurring also in the Australian Tertiaries. All of the Euro- 

 pean species are from the rocks (none from amber), and most have been 



