342 J. 8. Diller — Origin of Paleotrochis. 



the investigations of Wadsworth, Williams, Bascom and others 

 it has been definitely settled that they are all acid volcanics. 

 These rocks in North Carolina are regarded by Mr. Holmes 

 as pre-Cambrian and since their eruption may have undergone 

 great changes like those of the South Mountain described by 

 Miss Bascom. Some of the supposed fossils are certainly 

 spherulites, and all of them may have been originally. Some 

 broken forms show motion in the mass after the spherulites 

 were developed. That Paleotrochis where most perfectly de- 

 veloped and composed of granular quartz is the result of 

 deposition, after the spherulitic growths about it and within it 

 had developed, there can be no question, but whether this depo- 

 sition followed soon after that of the spherulites in the course 

 of solidification or took place in hollow spherulites (lithophysae), 

 or resulted perhaps long subsequently at the time of rock altera- 

 tions, is not so clear. All this and much more will doubtless be 

 cleared up by the members of the Geological Survey of North 

 Carolina, who were the first to correctly identify the rock and 

 the character of the supposed fossil. 



None of the Mexican specimens received from Prof. Wil- 

 liams were cut for microscopical examination. Some of them 

 Avere clearly of igneous origin, and contained amygdules. The 

 Paleotrochis-like forms with radial markings appeared to be 

 composed of secondary quartz and probably originated as those 

 of North Carolina. 



About a year ago bi-conical forms like Paleotrochis were pre- 

 sented by Mr. Kochibi, Director of the Geological Survey of 

 Japan, to the U. S. Geological Survey. These specimens are 

 now in the National Museum, and are much more regular in 

 form, size,- and general appearance than the Paleotrochis of 

 North Carolina. They are of a pale pink color with regular 

 bi-conical, striated forms, and in some cases have shallow pits 

 in one of the apices. They are known in Japan as "Soroban 

 ishi" or abacus stones. One of these specimens contains a 

 small fragment of the rock from which these curious specimens 

 were obtained, and it appears to be spherulitic. According to 

 Mr. Willis, who obtained the information directly from Mr. 

 Kochibi, " these stones are found only in rhyolitic tuffs. They 

 not infrequently occur much larger than these specimens, pos- 

 sibly up to two inches in diameter or more, and are more fre- 

 quently associated in groups of two or three overlapping or 

 coalescing. They are generally white, the rosy tint of these 

 specimens being a rare characteristic." A thin section of one 

 of these " abacus-stones " shows it to be an agate of which the 

 outer layers are pink and the inner white. There can be no" 

 doubt in this case that the form resulted from the filling of the 

 cavity long after the solidification of the igneous material. 



U. S. Geol. Survey, Washington, D. C, March 3, 1899. 



