the flora. 



151 



emerging at a low angle, camptodrome, often 

 forking a-t about one-third their length from 

 the margin, curving just inside the margin and 

 each joining the one next above; additional 

 shorter secondaries frequently interspersed be- 

 tween the principal ones, thence running one- 

 third or sometimes more than half the distance 

 to the margin, becoming obsolete or curving 

 downward and each uniting with the secondary- 

 next below; nervilles strong, percurrent, some- 

 times crossing at right angles to the second- 

 aries, but oftener oblique to them; finer 

 nervation mostly obsolete. 



This species is represented by the examples 

 showing the compound nature of the leaves 

 and by ten or more detached leaflets. The 

 largest specimen with the leaflets attached 

 has a rachis 3.5 centimeters long, and the 

 terminal leaflet has a petiole about 6 milli- 

 meters long. All the leaflets in this specimen 

 are broken, but they must have been at least 

 5 centimeters long and about 2.5 centimeters 

 wide. In the smaller specimen in which the 

 leaflets are attached only about 5 millimeters 

 of the rachis is preserved, and the petiole of 

 the terminal leaflet is only about 2, millimeters 

 long. These leaflets are much narrower than 

 those in the other specimen, the terminal one 

 being long, narrowly wedge-shaped at the 

 base, and the lateral ones very much narrowed 

 on the upper side. They must, however, 

 belong to the same species as the larger one. 



The numerous detached leaflets all appear to 

 have been lateral ones, as they are strongly in- 

 equilateral. Several of them are hardly to be 

 distinguished from the lateral leaflets in the 

 larger specimen mentioned above. 



Pistacia eriense is obviously related to and 

 possibly identical with P. hotticM, described 

 below. They come from the same locality and 

 have many points in common, the principal 

 difference being that the leaves of P. eriense are 

 odd-pinnate and those of P. hollicki abruptly 

 pinnate. This character, however, does not 

 hold in the living species, as pointed out in the 

 description of P. hollicki, but I have decided 

 to keep them separate, provisionally, even on 

 the slight grounds mentioned. There are also 

 minor differences in size and nervation. 



Occurrence: Laramie formation, Erie, Colo. 



Pistacia hollicki Knowllon, n. sp. 



Plate XXVIII, figures 5, 6. 



Pistacia hollicki Knowlton [nomen nudum], U. S. Geol. 

 Suryey Bull. 696, p. 460, 1919. 



Leaves compound, abruptly pinnate; rachis 

 slender; leaflets nearly sessile, oblong-lanceo- 

 late, entire, inequilateral on the upper side, 

 slightly rounded or wedge-shaped at the base, 

 abruptly acuminate at the apex; midrib of 

 leaflets strong, secondaries numerous, 10 to 12 

 pairs, alternate, emerging at a low angle, 

 craspedodrome, frequently forking near the 

 margin; which they enter; tertiaries usually 

 midway between the secondaries, slender, run- 

 ning halfway to the margin and. disappearing 

 or bending downward and each joining the 

 secondary next below; nervilles rather strong, 

 percurrent, running obliquely between the 

 secondaries; finer nervation not retained. 



This beautiful species is represented by three 

 specimens and seven or eight leaflets, all well 

 preserved. The larger example has the rachis 

 preserved for 2.5 centimeters. The terminal 

 leaflets are sessile and exactly opposite. They 

 are very inequilateral, the upper side near the 

 base being reduced quite to the midrib. They 

 appear to have been about 3.5 centimeters long 

 and are about 1.5 centimeters wide in the 

 broadest part, which is above the middle. 

 The lateral leaflet is 7 millimeters below the 

 terminal ones and has a petiole scarcely 1 mil- 

 limeter long. It is more nearly oblong-lan- 

 ceolate and is 3.5 centimeters long and 13 

 millimeters wide. Like the terminal ones, it 

 is inequilateral, , but not to the same extent. 



The other example figured has three leaflets 

 preserved, "but the point of their attachment 

 can not be made out. They are shorter than 

 those of other specimens, being only 3 centi- 

 meters long. They have the same nervation 

 as the others. 



It is with considerable certainty that these 

 leaves are referred to the genus Pistacia, for 

 in the manner of arrangement and shape of 

 leaflets and nervation they approach closely 

 certain living species of the genus. In the 

 abruptly pinnate character of the leaves, as 

 well as in the shape of the leaflets, they are 

 similar to P. lentiscus LinnS, a species of 

 southern Europe. They approach more closely, 



