EXPLANATION OF PLATES. 



PLATE I. View of Eagle Crag, on Pine Ridge, near Harrison, Sioux 

 Co., Nebraska, from the west, showing fossil corkscrews at various levels. 

 Two workmen may be seen, one above, the other below. A large view of 

 the latter may be had in Plate VII. Surface and minute structure may be 

 seen in Plate VIII. 



PLATE II. Fig. 1 — Portions of a large Diainonelix, showing gross 

 structure, which consists of an interminable tangle of ramifying tubules. 

 The general surface presents a corrugated appearance. Fig. 2 — A view 

 of the surface structure of the above, reduced about one-half. Fig. 3 — 

 Section cut from the above, showing microscopic structure. 



PLATE III. Fig 1 — Diamonelix as found weathered out. Fig. 2 — 

 section across the same, as indicated by dotted line, showing white wall 

 and, lesser and greater tubules. Fig 3 — A section cut from the thickened 

 wall of Fig. 2, showing cells in longitudinal section. 



PLATE IV. A portion of a large Diamonelix enclosing the bones of a 

 Mammal. The femur, tibia, calcaneum, part of ilium, and a series of 

 twelve or fourteen vertebrae are partly worked out. Length of femur, 

 13 inches; length of tibia, 10 inches. 



PLATE V. View of a pair of fossil corkscrews as they appeared when 

 partly worked out. Height, 7 feet 9 inches. 



PLATE VI. View of a fossil corkscrew in bluffs near the Niobrara 

 River, showing students at work. 



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