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208 FOSSIL TURTLES OF NORTH AMERICA. 
structure resembles that of the pelvis of the Cheloniidz, but it differs in having a median 
bridge of bone connecting the pubes and the ischia. In this way ischio-pubic foramina are 
formed, but they are of small size. As stated by Wieland, the extreme antero-posterior length 
of the pelvis is 970 mm.; the extreme width, 810 mm. The fore-and-aft length of the pubis 
is 460 mm. The length of the ilium is 300 mm., and its diameter, at the middle of the shaft, 
is 105 mm. 
The femur (fig. 267, fe) has the ratio to the humerus that it has in Caretta caretta. Its 
extreme length is 460 mm. The tibia (fig. 267, 7b) has a length of 330 mm.; the fibula (fig. 267, 
fib) a length of 310 mm. 
As in the case of Protostega, we can not doubt the adaptation of this turtle to marine 
aquatic life. Its excursions on land must have been confined to those for the deposition of 
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Fic. 268.—Archelon tschyros. Pelvis seen from below. 1o. 
1], ilium; fp, ischio-pubic foramen; fsch, ischium; pub, pubis. 
its eggs. We can only speculate as to what extent it spent its life on the high seas away from 
the coasts. It seems probable that the broad and heavy body and the ponderous head were 
obstacles in the way of sustained journeys over rough seas. Its prolonged beak, furnisht 
with a broad crushing-surface, appears to indicate a diet, not of soft and actively swimming 
animals, but of mollusks and crustaceans. Associated with the fossil were various genera of 
tetrabranchiate cephalopods, and the jaws of the turtle seem to have been admirably adapted 
to pick up and crush such objects. 
Archelon marshi Wieland. 
Archelon marshit, WieLanp, Amer. Jour. Sci. (4), IX, 1900, p. 248; ibid., xv, 1903, p. 215.—Hay, 
Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 440. 
This species was secured by Wieland in the upper beds of the Pierre formation, in South 
Dakota, on the east side of the South Fork of the Cheyenne river. It is described in the 
briefest terms. The remains are stated to consist of the plastron, the humerus, ribs, and a 
number of peripherals. These indicate a turtle about 11 feet in length. The humerus is 
said to be rather straighter than that of 4. rschyros and the plastron relatively more massive, 
being fully one-half thicker than in the latter species. 
Family CHELONIID Gray. 
Thecophorous turtles fitted for life on the sea. Skull with temporal region extensively 
rooft over. No nasal bones. No posterior palatine foramina. Quadrate notcht behind for 
