764 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



cells are always smaller than the ordinary ray cells. The number of 

 cells making up each ray ranges from 2 to 30 or more, but the average 

 number is about 8 to 15. 



The rays in which there is a resin duct are rather rare. The duct is 

 large, taking up all the width of the ray. The remainder of the ray is 3 

 rows of cells high in the middle and is reduced to 1 at the extremities. 



The wood cells show clearly in this section. They are not provided 

 with pits or other markings. 



Habitat: Specimen Ridge, Fossil Forest, near head of Crystal Creek; 

 collected by F. H. Kuowlton, August, 1887. Yancey Fossil Forest; col- 

 lected by F. H. Knowlton, August, 1887. 



PlTYOXYLON AMETHYSTINUM U. Sp: 1 

 Pis. CVII, CVI1I, OXIV, CXV, CXVIII, figs. 1, 2. 



Diagnosis.— Trunks of small or medium size ; annual rings sharply 

 demarked, 3 to 8 Jinn, broad; resin ducts numerous, scattered, but mainly 

 in fall wood; wood cells long, sharp-pointed, provided with a single row of 

 scattered, small, somewhat irregular pits; medullary rays numerous, in a 

 single series of 2 to 12 cells, the average being about 5 or 6. 



Transverse section. — Much like the preceding species, except that the rings 

 are narrower, the cells of spring and summer wood are smaller, and the 

 late fall cells have thinner walls. The resin ducts are also much the same, 

 being in general only a little smaller. A few are found iu the summer 

 wood, but most of them are in the fall wood. The rays are not nearly so 

 numerous as in the last species. They are often separated by as many as 

 25 rows of wood cells. 



Radial section. — The radial section of nearly all woods from the Yellow- 

 stone National Park is more or less obscure. The one under consideration 

 is no exception to this rule, and it is only after considerable search that the 

 pits can be determined. They are in a single row (see PI. CXVIII, fig. 1) 



1 Iu 1888 Dr. J. Felix, of Berlin, visited, and collected fossil wood in, the Y'ellowstone National 

 Park. The results of his work were published iu Zeitscbrift der Deutschen geologischen Gesellschaft, 

 for 1896. He described six species of fossil wood, of which uuuiber I have recognized four. The 

 following two species were uot figured, and as the locality w^hence they came is more or less in doubt 

 I have not included them in the systematic enumeration. They are as follows: Pityoxylon fallax and 

 Cvpressinoxylon eutreton. They may be identical with certain of the species I have described, but of 

 this I am uncertain, 



