THE 
AMERICAN NATURALIST. 
Vor. xx.—/ANUARY, 1886.—No. I. 
BOULDER MOSAICS IN DAKOTA. 
BY PROFESSOR J. E. TODD. 
os eee a name seems best to express the character of certain 
strange works noticed by the writer upon some of the con- 
spicuous hills of Southeastern Dakota. The term mosaic, though 
describing better than any other word their structure, may sug- 
gest greater delicacy than they possess, but the qualifying epithet 
sufficiently corrects it. 
A typical example, and the first to come to the writer’s knowl- 
edge, was found on the summit of Keya Kakop, or Turtle point, 
three miles north of Wessington springs in Jerauld county. The 
point is a high promontory-like hill standing out on the western 
edge of the James River valley, above which it rises nearly 500 
feet. It is the northern end of a high ridge of drift constituting 
a well washed interlobular portion of the principal moraine. A 
view of Turtle point and a portion of the ridge from the north- 
west is shown in Fig. 1. Upon the highest portion of the point ` 
~is a low broad mound built of earth, perhaps fifty feet in diame- 
` ter andthree or four feet high. It does not differ materially from 
many that are found on the summit of bluffs along the James and- 
Missouri. Its chief attraction is the gigantic figure of a turtle 
upon its southern slope, as is shown in Fig. 2. This figure is 
formed of boulders, four to six inches in diameter, quite closely — 
and regularly set, so as to describe its outline. The head, legs 
< andtailare extended. Its general appearance, position and struc- 
ture are shown in Fig. 3. Visitors to the locality will also- notice 
a rude human figure, sketched with similar material, on the 
south-west side of the mound as shown in Fig. 2, but it is cón- 
fessedly the vork of an earl owner of the | . 
VOL, XX —No, I, 
To ome ae 
