APPENDIX TO THE REPORT OF THE SECRETARY. 71 



Wiud Eiver, Bull Lake, DiiiwicUlie, and Torrey's Forks, only less ex- 

 tensive accumulations of glacial materials than those found along- the 

 west border of the range. 



In the water-shed extending northward from the northern end of the 

 Wiud Eiver Kange extensive arenaceous deposits of modern-looking 

 Tertiary age but slightly disturbed, are met with, and which evidently 

 form uninterrui)ted connection with the Wind Eiver Tertiaries on the 

 one hand and the deposits which occui^y so large area east of Jackson's 

 Basin on the other. In the latter quarter, in the Mount Leidy high- 

 lands, and along the upper courses of the main tributaries of the Gros 

 Ventre, in lower strata of the same series, extensive developments of 

 lignite were met with, the special investigation of which was undertaken 

 by 3Ir. Perry. In still more ancient horizons other lignitic seams were 

 found which, together with those just mentioned, render this one of the 

 most important coal-i)roduciug areas as yet discovered in this region. 



In the latter region the lignitic and older mesozoic formations within 

 a narrow belt at the northern foot of the Gros Ventre Mountains have 

 been thrown into a series of sharj) j)arallel folds. To the northeast the 

 Tertiaries dip, with gradually slackening inclinatiou, until they pass be- 

 neath the volcanic mantle in the vicinity of Togwotee Pass ; on the op- 

 posite side the older Mesozoics as uniformly rise up on the flank of the 

 Gros Ventre Mountains, whose northern crest reveals the regular 

 courses of the Carboniferous limestone which in i)laces preserves a cop- 

 ing of the Triassic " red beds." 



During the last two months the expedition encountered much in- 

 clement weather, embarrassing the prosecution of the field-work; aud 

 on its arrival in the region of JMount Leidy and Buffalo Fork, about the 

 middle of October, it was overtaken bj' the early snows of winter, which 

 virtually closed the field-work for the season. 



Paleontology. — So large an amount of i^aleontological material hr.d 

 accumulated during the previous years that its critical study became 

 necessary for the purpose of aiding in the elucidation of certain problems 

 in structural geology which had arisen in the prosecution of the field- 

 work. Dr. C. A. White, paleontologist to the survey, therefore deyoted 

 the whole season of 187S to this work at the ofiice, instead of takijng the 

 field as he did the previous season. The work which thus engaged his 

 attention embraces the preparation of a detailed report of his field work 

 for 1877, including the discussion of important questions conne(;t<^d with 

 it, the preparation of a large number of new fossil invertebrates for 

 publication and illustration, and the illustration of all the types of 

 species in the collections of the survey which the late Mr. F. B. Meek 

 had described, but not illustrated. 



Besides the collections made ])y the various parties of the survey, 

 others have from time to time been received from several persons not 

 ofiicially connected with it, from ditterent parts of the western portion of 

 the national domain. The investigation of these collections brings out 



