The Geological Society of Amci'ica. — Hovey, 97 
Museum. Accepting the conclusions of Lindgren, Turner, and other ge- 
ologists concerning the origin and age of the auriferous gravels, the 
authors described the deposits, tlie subsequent erosion by which they 
have been reduced to remnants, and the principal events in the geo- 
logic history of the region. Beginning with the base-leveled surface 
of a peneplain in early or middle Tertiary time, the region was ap- 
parently depressed and tilted westward in such manner that a number 
of parallel streams (prototypes of the present waterways) clogged 
their channels with beds of coarse gravel derived from the ancient 
Sierra rocks; later vulcanism. supervened , and some of the water- 
ways were further choked by the ejectamenta in such manner that 
tufif-beds, interspersed with gravel-deposits, were accumulated, while 
the accumulation ended, in some portions of the region, with out- 
flows of andesitic and basaltic lavas. Afterward the region was lifted, 
and profoimd canyons were carA^ed by the rivers draining the western 
slope of the Sierra: most of the preceding deposits were carried away, 
a few remnants only persisting in the form of table mountains, elevat- 
ed tuff-beds, and gravel-streams, generally overlain by lavas and tuffs, 
while in the typical part of the region, the cutting extends from one 
thousand to three thousand feet below the Tertiary gravels, tuffs, 
and lavas, and into the obdurate rocks of the Calaveras and Mariposa 
formations. The fossils and relics recorded from the gravel-beds were 
•described as (i), plant fossils; (2), animal remains; (3), mortars, 
pestles, and other stone artifacts, and (4), human bones. The plant 
remains have been found in limited quantity in a number of localities, 
usually in fine beds associated with the gravels and tuffs; they indicate 
ages ranging from about middle jNliocene to late Miocene or early 
Pliocene. The animal remains are much fewer, but their testimony 
as to age coincides with that of the plants. The stone artifacts, all 
belong to a single cultural type — the type represented by the living 
Indians of the region (commonly known as Diggers), whose chief 
food-source is the acorn; their habits of life, including most of their 
industries, much of their language, the essential features of their 
social organization, and the distinctive features of their religion are 
adjusted to this food-source; they are as completely acorn Indians 
as the Dakotas were buffalo Indians. The implements used by them 
to-day, in making acorn-meal, are indistinguishable in material, form, 
and mode of preservation from those reported to have been found 
in the gravels associated with and commonly below the Tertiary lavas 
and tuffs. The only fully recorded occurrence of human remains in 
the gravels below the lava, is the case well known to geologists as 
the Calaveras skull. This fragmentary cranium has not been examined 
critically by the authors; but comparison of Whitney's reproductions 
of this specimen with related material in the National Museum in- 
dicates that it is to all appearances a normal Indian skull. The authors 
described their visit to the locality whence this specimen was re- 
ported, and their conferences with the dozen or more surviving min- 
ers and business men who were personally acquainted with the cir- 
