DARTON, N.H. - Geology of the Bighorn Mountains. [Wyoming and Montana]

1906. US Geol. Surv. Prof. Paper 51; 129 pp. 1 fig. 46 plts. h.t. (1 col. mostly phot.), 3 fold. & col. plts. with geol. maps and sections loosely inserted in back pocket. Orig. wrps. with faint libr. stamp, spine repaired with paper tape, margin of covers a bit frayed, sides of pocket cut open, otherwise and contents very good, colour plates crisp and clean, 4to.