LETTER OF TRANSMITTAL. 



U. S. GEOLOGICAL SURVEY, 



DIVISION ov FOSSIL INSECTS, 

 Cambridge, M.ml, 1 1, ix<0. 



SIR: It is a source of great regret t> me that the- volume herewith trans- 

 mitted could not have been published during 1 >r. Ilayden's lite ll con- 

 tains the tirst fruits of an undertaking inspired by him and encouraged bv 



his aid. The- extent of the task he intni.Med to me re than a dozen years 



ago lias been, with the, intert'erence of other duties, the occasion of the 

 dela\ in it> execution. The material has grown beyond all expectation, far 

 be\ 1 an\ thing that could have lieeii antiei]iateil. 



4s originally planned, when the Florissant beds were first carefully 

 exploited, the fossil insects other tjian those from Florissant were first to be 

 disposed of, and the latter were then to be taken up by orders. The plates 

 were accordingly executed (before the completion of the text) with that 

 plan in view, and the first ten plates herewith transmitted contain very 

 nearly all the extra-Florissant insects known ten years ago. Since then 

 their number has perhaps doubled. The succeeding- plates contain the h>\\ ei 

 orders of Flori>-ant arthropods, ending with the Ilemiptera. 



The text has been made to conform in large measure to the same plan, 

 except that the insects of different localities and of different horizons have 

 been arranged in one systematic series. Descriptions of a considerable 

 number of species have been introduced for completeness' sake which are 

 not figured, but of every one of these drawings have been finished and will 

 be given in some future publication. The early portion of the text was 

 written many years ago the Arachnida and Termitina in 1881, most of 

 the Odonata in 1882, the Ephemeridae and Planipennia in 1883, and the 

 Trichoptera and Orthoptera in 1884; and, as the general remarks prefixed 

 to each group were written on the completion of the study of that group, 

 and would now have to be modified in some slight particulars, I have 



thought best to let these remarks remain as written, and to append at the 



n 



