726 IDAHO MINING DISTRICTS. 



strong; secondaries about four or five pairs, the lowest pair arising 

 from the very base of the blade, thin, soon lost in the blade ; second 

 pair very strong, arising from the petiole some distance above the 

 base and arching up for two-thirds the length of the leaf, probably 

 branched outside; the other secondaries, probably two or three pairs, 

 arising some distance above, strong, alternate, at an angle of 45 ; 

 finer nervation not retained. 



This well-marked species is represented by the four specimens fig- 

 ured. The larger of these (fig. 2 of PL CI) is 10.75 cm in length with- 

 out the petiole, which is 5.25 cm long. The margin is not all preserved, 

 but the leaf appears to have been about 7 cm in width. The other 

 nearly perfect leaf (fig. 1) is a little less than 10 cm in length -and is 

 6.5 cm in width. About 3.5 cra in length of petiole is preserved, but it 

 is not all present. 



The leaves are all broadly ovate, with rounded bases and obtuse 

 apices. The margin is crenate-toothed from above the base. The 

 petiole is very long, as may be seen from the figures, and is obviously 

 flattened. The nervation is not well preserved, but enough can be 

 made out to show its general character. The strong pair of second- 

 aries arise some distance above the base, while the thin basal pair 

 arise near the top of the petiole. There are also two or three pairs of 

 secondaries arising from the midrib some distance above the strong 

 pair. None of the ultimate nervation is retained. 



Among living species the relation of this fossil form is unquestion- 

 ably with P. tremuloides Michx. In the herbarium of the National 

 Museum there is a specimen, consisting of a young seedling plant of 

 this species, collected on the Aquarius Plateau, Utah, at an altitude 

 of 9,000 feet, that can hardly be distinguished from the fossil leaves 

 under consideration. The size, outline, petiole, and nervation are 

 practically identical. The only difference, and this is of minor im- 

 portance, appears to be in the margin. In the fossil form the teeth 

 are absent from the lower fourth of the leaf, while these specimens 

 of P. tremuloides are toothed from base to apex and the teeth are 

 rather larger. The leaves of this seedling differ somewhat from the 

 normal mature leaves of the species, but it would seem, in view of 

 their evident relationship to the fossil leaves, that they represent a 

 reversion to an ancestral type, or perhaps rather a survival of this 

 type, which disappears in the mature plant, There certainly can be 

 no doubt of the intimate relationship between the living and fossil 

 leaves. 



There seems to be no fossil American species with which it is at all 

 intimately related. It is perhaps closest to P. zaddachi Heer, but 

 differs markedly. 



I have given this species the name eotremuloides in view of its 

 evident relation to the well-known tremuloides. 



. Locality: Two miles southeast of Marsh post-office, Boise County, 

 Idaho. 



