ELISHA MITCHELL SCIENTIFIC SOCIETY 60 
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,' after an examination of many specimens, 
regarded the Paleotrochis of Emmons as nothing but concre- 
tions in quartz rock. Prof. O. C. Marsh’ 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 dif- 
ficult 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 preplexing form is that 
of Mr. C. H. White,’ who strongly advocates the organic 
nature of Paleotrochis. The specimens he examined were 
those obtained by Prof. Emmons, as well as a number col- 
lected by Prof. J. A. Holmes, the present State Geologist of 
North Carolina. Mr. White describes in detail not only the 
peculiarities of the weathered surface of the rock but also the 
features exhibited upon a fresh fracture, and called attention 
1 Am. Jour. Sci., II, vol. xxiii, page 278. 
_ 2 Am, Jour. Sci., Il, vol. xlv, page 218. 
3 This Journal 1894, Pt. 2, 50-66. 
