12 LETTER OF TKANSMITTAL. 



end of each general paragraph the date of writing. To rewrite the whole 

 would unnecessarily delay the appearance of the work, and the dates will 

 explain otherwise unaccountable, though generally very slight, omissions of 

 later material. 



The new portions of the Coleoptera, Diptera, and Hymenoptera were 

 mostly written a year ago, and during the past year the Hemiptera, much 

 the most extensive group in the volume, have been elaborated. In the four 

 later orders the general remarks and summaries attached to the genera, 

 families, etc., of the earlier groups are omitted, because these orders will 

 form the subject of future separate consideration, and the basis for generaliza- 

 tion will then be greatly increased; the representation of these orders in the 

 present volume is very meager, including next to no species from Florissant. 



The publication of this volume will give the first opportunity for any 

 good comparisons between the long known Tertiary insects of Europe and 

 those of any other country; .so far as the lower orders of insects are con- 

 cerned the only ones here at all fully elaborated they show that the ma- 

 terial already gathered within the last two decades in America is at least as 

 rich as that of the well gleaned fields of Europe. The present volume con- 

 tains descriptions of 1 species of Myriapoda, 34 of Arachnida, 66 of Neu- 

 roptera, 30 of Orthoptera, 266 of Hemiptera, 112 of Coleoptera, 79 of Dip- 

 tera, 1 of Lepidoptera, and 23 of Hymenoptera, in all 612 species. For 

 the lower orders, that is, those here fully treated, these numbers are already 

 slightly in excess of those obtained from the European Tertiaries, if the rich 

 amber fauna of the Baltic is excluded; for the corresponding numbers for 

 the European species from the rocks would be approximately as follows : 

 Myriapoda, 1 ; Arachnida, 24 (recently, however, nearly doubled); Neu- 

 roptera, 59; Orthoptera, 36; arid Hemiptera, 218; a total of 338 species 

 against 397 for the American rocks. There is no doubt that this excess 

 would be found even greater in the higher orders by the material already 

 many years in hand ; and the extent of the insect-bearing rocks of the 

 West, which as yet have been touched only here and there, is so immeas- 

 urably greater than that of similar European strata that only the lack of 

 students in this field of American paleontology can prevent our deposits 

 from assuming a commanding position in the world. 

 Very respectfully, yours, 



SAMUEL H. SCUDDER. 



Hon. J. W. POWELL, 



Director U. S. Geological Survey, Washington, D. C. 



