504 



SCIENCE. 



[N. S. Vol. XVIII. No. 459. 



the latter being from other evidence less prob- 

 able. 



The spheroids are a brilliant white in 

 color and resemble albite alone, but the micro- 

 scopic examination reveals considerable ortho- 

 clase in addition to the plagioclase, and also 

 much quartz. The quartz fills interstices be- 

 tween the feldspars. The extinction of the 

 plagioclase upon flakes parallel with the basal 

 pinacoid is so slight that the species is in 

 large part oligoclase, but the thin sections 

 give ground for believing albite also to be 

 present and possibly varieties even more basic 

 than oligoclase. The reflections which are 

 given by some broken nodules show that in 

 instances much the greater portion consists 

 of a single feldspar crystal. Others have but 

 few, relatively large individuals; and still 

 others are radiating aggregates. Where the 

 constituent feldspars are coarse and few the 

 core is marked by a few flakes of black 

 biotite irregularly disseminated. They then 

 cease and the main mass of the nodule is 

 feldspar. Even the core may itself practically 

 fail, the nodule becoming a mere ellipsoid 

 of feldspar. 



Where the core is well developed it. is due 

 to a considerable richness either of biotite or 

 hornblende, both having been observed, but 

 each in different spheroids. They may, how- 

 ever, and probably do occur together. Well- 

 marked rings of biotite or hornblende may 

 also appear half way or two thirds the way 

 from the center to the circumference. 



There is no marked outer border to the 

 nodules such as appears in other cases, the 

 contrast being due to the fact that the gen- 

 eral matrix is a very dark aggregate of biotite, 

 hornblende, the two feldspars and quartz. 

 The dark minerals are in very large amount, 

 so that the brilliant white nodules stand out 

 with great distinctness. 



It appears from the relations of the min- 

 erals that the dark silicates first crystallized, 

 together with some feldspar and quartz, and 

 formed the cores. Next followed a period of 

 formation of little else than feldspar and 

 quartz, varied occasionally by a slight separa- 

 tion of the dark silicates. Finally the residue, 



greatly impoverished by the loss of so much 

 of the feldspathic material, crystallized as the 

 dark matrix. 



During the crystallization the pegmatitic 

 streak also formed, and along its borders de- 

 veloped in part as half spheroids. It does not 

 appear to be a phenomenon subsequent to the 

 development of the nodules, and is not very 

 sharply delimited from the spheroidal rock. 



The home of the boulder lies somewhere to 

 the north, probably in Ontario, but, so far as 

 known to the writer, no similar rocks have 

 yet been recorded in this region. Acknowl- 

 edgments are due, in closing, to Professor A. 

 W. Grabau, through whose kind ofiices the 

 material was secured. J. F. Kemp. 



Columbia University. 



present knowledge of the distribution of 

 daimonelix. 

 Daimonelix when first discovered, in 1891, 

 was thought to be confined to the elevated 

 tablelands of central Sioux County, Nebraska. 

 In the meantime its range has been extended 

 and it is now known almost throughout the 

 entire Arikaree fOTmation, a tract probably 

 about five hundred miles in diameter, situ- 

 ated in Nebraska, Kansas, South Dakota, Wy- 

 oming and Colorado. The more fibrous forms 

 of Daimonelix constitute a character so con- 

 stant as to justify the name Fibrous Arikaree 

 for the upper half of the formation. The 

 writer has traced these fossils as represented 

 by the fibrous forms as far south as Benkle- 

 man, on the Kansas-Nebraska line, as far east 

 as Fullerton and Long Pine, Nebraska ; as far 

 north as Eagle Nest Butte and White Clay 

 Butte, in the Sioux Indian Reservation m 

 South Dakota; and as far west as Lusk, 

 Guernsey and Bates Hole, in Wyoming. Well- 

 authenticated reports would include north- 

 eastern Colorado, but those places only are 

 mentioned which have been visited personally 

 by the writer. Daimonelix proper is much 

 more restricted than are the fibrous forms. 

 However, its range has been extended be- 

 yond the highlands of central Sioux County 

 as far west as Lusk, Wyoming, and as far east 

 as Eagle Nest Butte, South Dakota. 



