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University of California. 



[Vol. 2. 



beds (in part), and the Amyzon* beds. Recently Wort man has 

 placed his palaeontological horizon, known as the Protolabisf beds 

 in this formation. None of these names appear to be applica- 

 ble to the formation considered as a stratigraphic unit. The 

 term Cottonwood is pre-occupied, having been used for a car- 

 boniferous formation by Prof. C. S. Prosser. It is very doubtful 

 whether it can ever be shown that this series and the true Loup 

 Fork occupy the same horizon in the standard geological scale. 

 As yet it has not been done. The Ticholeptus beds probably 

 belong to another horizon than the one with which we are dealing. 

 The correlation of this series with the Amyzon beds was due to its 

 confusion with the Clarno at Bridge Creek. Wortman's Protolabis 

 beds will doubtless be found to cover a considerable portion of this 

 formation, but as the section is perhaps a thousand feet or more in 

 thickness it is almost probable that it will be found to represent 

 more than one palaeontological horizon. It is, moreover, advisable 

 to separate palaeontological horizon names from those used for 

 formations or stratigraphic units. It is, therefore, proposed to des- 

 ignate these beds as the Mascall formation. The typical exposure 

 is near the Mascall Ranch, four miles below Dayville. 



Occurrence and Stratigraphic Relations. — In the valley of the 

 East Fork the Mascall formation rests in the depression formed by 

 the deflexed Columbia lavas. (See Fig. i.) The dip of the lower 

 beds is here approximately the same as that of the lava beds below 

 them; the uppermost strata may be slightly flatter. On Birch 

 Creek and at several other localities, there is some evidence of 

 intercalation of lava flows between the lower strata. The Mascall 

 beds do not reach to the level of the lava plateau to the north, 

 though they may formerly have passed over it. They have suf- 

 fered much erosion and a later formation rests upon their worn 

 edges. So far, the writer has learned of no deposits corresponding 

 to the Mascall in the northern part of the basin. The Ellensburg 

 beds of central Washington, described by Russel,| are probably 



*E. D. Cope, Pruc. Am. Phil. Soc, 1880, V. 19., p. 61. 

 tj. L. Wortman, Bull. Am. Mus. Nat. Hist., V. X, pp. 120, 141. 

 J Bull. 108, U. S. Geol. Surv., p. 22., also 20th Ann. Rep., U. S. Geol. 

 Surv., Part II, p. 127. 



