Subsurface Laboratory Methods 113 



(See fig. 49.) In abstract he says: 



The most common among these fossil seeds show close relation to the 

 most typical modern prairie grasses. . . . Comparative study of the fossil and 

 living forms reveals evolutionary trends of the seeds of prairie grasses. The 

 rather small and generalized Miocene ancestor gave rise to greatly diversified 

 Pliocene and Recent species. The seeds of these include small and very large, 

 very slender, and very stout forms, all of them variously adapted for protection 

 against drought and for more efficient dispersal. Abundance, good preserva- 

 tion, and rapid ecologic and evolutionary changes make grass seeds the best 

 index fossils for subdivision of the continental Late Tertiary rocks. 



Fish Scales 



Fish remains, especially fish scales, commonly occur in sediments. 

 In the Pacific Coast Tertiary section, according to David,-^ a 



. . . great number of fish scales can be used characteristically as index or 

 marker fossils. Others occur in well-marked abundance zones, indicating in 

 that way horizons of definite age and making it possible to correlate quite 

 accurately. . . . Scales of different kinds of fishes show innumerable variations 

 of their ornamentation, of the designs and angles formed by the fingerprintlike 

 impressions that mark the scales. . . . Herrings and round herrings are the 

 most abundant scales through the Tertiary. ... A number of very distinct 

 scales are of importance for paleoecological determinations. . . . These fossil 



EXPLANATION OF FIGURE 49 



Magnification 

 Nos. 1, 3, and 10, X 3; No. 4, X 33; No. 5. X 29; Nos. 6-9, 11-16, X 15. 

 Fossil Panicum elegans early mutation nebraskense ; Panicum elegans; Setaria 

 chasea. Living Panicum angustifolium; Setaria chasea. Living Panicum angus- 

 tifolium; Setaria crusgalli; S. glauca. 

 Nos. 



1,2. Panicum elegans Elias, early mutation nebraskense Elias n. mut.; basal part 

 of Biorbia fossilia zone, Ash Hollow formation, Ogallala group; east of rail- 

 road bridge, Wi miles west of Wauneta, Chase County, Nebraska; middle 

 Pliocene. 



3, 4. Panicum elegans Elias. 3, Autotypes, about seventy feet below the top of the 

 local section of Ogallala, two miles east-northeast of Ogallala, SE%, sec. 33, 

 T. 14 N., R. 38 W., Keith County, Nebraska. Both from upper part of Biorbia 

 fossilia zone. Ash Hollow formation, Ogallala group; middle Pliocene. 4, 

 Holotype, showing epidermis of palea, from about forty feet below algal 

 (Chlorellopsis) limestone (at top of Ogallala group), sec. 21, T. 14 S., R. 39 

 W., Wallace County, Kansas. 



5. Living Panicum angustifolia Elliott; eastern United States. 



6-8. Living Echinochloa crusgalli (Linne) Beauvois; from Mexico. 

 10-14. Chaetochloa chasea Elias, n. sp.; syntypes; west of United States Department 

 of Agriculture Experiment Station at North Platte, Lincoln County, Nebraska. 

 Upper portion of Ogallala group above Biorbia fossilia zone. Collected by 

 H. E. Weakly. 11, showing tripartite apex of the lemma; back view. 12, show- 

 ing frontal view of upper part of hull, palea parting from lemma; uppermost 

 middle Pliocene or upper Pliocene. 15-16, living Chaetochloa glauca; from 

 near Almera, Himalaya Mountains. Note slight parting of lemma and palea 

 in No. 15; also similar type of sculpture of both lemma and palea with 

 Setaria cahsea Flias. 



^^ David, L. R., How Fossil Fish Remains Have Been Used in Pacific Coast Stratigraphy: Petroleum 

 Eng., vol. 18, no. 8, pp. 104-113, May 1947. 



