J. 8. Diller — Origin of Pcdeotrochis. 337 



Art. XXXYII. — Origin of Pcdeotrochis ; by J. S. Diller. 



Prof. Ebenezer Emmons,* while State Geologist of North 

 Carolina, discovered among the so-called Taconic rocks of 

 Montgomery County, in that State, a number of more or less 

 regularly striated bi-conical forms to which he gave the names 

 Paleotrochis major and minor, and regarded them as siliceous 

 corals as well as the oldest representatives of animal life 

 upon the globe. According to Emmons Paleotrochis varies 

 in size up to two inches in diameter, and occur with 

 many almond shaped concretions, often within concretions, in a 

 series of beds over 1,000 feet in thickness interstratified with 

 beds of granular quartz, conglomerate and quartzite. Both 

 species of Paleotrochis have the form of " a flattish double cone 

 applied base to base" with the surfaces grooved somewhat 

 irregularly from near the apex to the basal edge. The smaller 

 form, P. minor, has the " apex of the inferior side excavated or 

 provided with a small roundish cavity" and the other apex 

 " supplied with a small rounded knob, from the base of which 

 the radiated grooves begin." The larger form, P. major, 

 " differs from the foregoing (P. minor) in the absence of the 

 roundish apical depression of the lower side and the knob of 

 the opposite side." 



• Prof. Emmons regarded Paleotrochis not only as originally 

 siliceous but also gemmiferous, thus accounting for knobs as 

 well as irregular adhering groups, and it is important to note 

 that he reports " these fossils also occur in a variety of quartz 

 or quartzite which I have described as a buhrstone, and which 

 is often porphyrized." 



Prof. James Hall,f after an examination of many specimens, 

 regarded the Paleotrochis of Emmons as nothing but concre- 

 tions in quartz rock. Prof. O. C. Marshy examined the forms 

 microscopically and found them composed of fine-grained 

 quartz, but no trace of organic structure could be detected. 

 While maintaining its inorganic nature he regarded it as diffi- 

 cult to explain, and considered it as having some analogy with 

 cone-in-cone, which he thinks is probably due to the action of 

 pressure on concretionary structure when forming. 



The most extensive paper on this perplexing form is that of 

 Mr. C. H. White,§ who strongly advocates the organic nature 



* Geological Report of the Midland Counties of North Carolina, 1856, page 62, 

 also this Journal, II, vol. xxii, page 390, and vol. xxiv, page 151. 



f This Journal, II, vol. xxiii, page 218. 



\ This Journal, II, vol. xlv. page 218. 



§ Journ. of the Elisha Mitchell Scientific Soc , Chapel Hill, N. C, Part 2d, July 

 to December, 1894, pages 50-66. 



