Association of American Geologists. 161 
indicate,) or as different members of one formation—the mountain lime- 
stone. 
In reply to some remarks by Prof. H. D. Rogers, Prof. Locke ob- 
served, that he did not undertake to be the advocate of absolute equiva- 
lency, but merely to point out the agreement and disagreement of certain 
formations in America with similar ones in Europe. . He was of opinion, 
however, that certain points of equivalency must be admitted, as for ex- 
ample granite, the great coal formations, &c. 
Prof. Mather proposed the subject of “Joints of Rocks” for 
discussion during this session of the Association; and Prof. H. 
D. Rogers proposed that of “ Fossil and Recent Infusoria.” 
The Association then adjourned until 4 o’clock this afternoon. 
April 6th, 1841, 4 o’clock, P. M—The Association met pur- 
suant to adjournment, Prof. Locke in the chair. 
Mr. William C. Redfield exhibited specimens of fossil shells, 
from the tertiary marl-beds at Washington, Beaufort county, 
North Carolina. 
Mr. R. stated that these beds, which are about sixty miles from the At- 
lantic, are found from fifteen to twenty feet below the adjacent surface, 
and two or more feet lower than the usual level of Pamlico river and 
sound. The fossils are in a good state of preservation, and are supposed 
to belong to the miocene period. : 
Prof. Locke read a paper “on anew species of Trilobite, found 
at Cincinnati, Ohio,” and called by him Isotelus maximus. 
This species is characterized by its elliptical terminations, and by a 
thorn-like process about one tenth of the length of the animal, projecting 
backwards from each angle of the shield, similar to an Ogygia. He ex- 
hibited casts of one entire specimen, nine and three fourths inches in 
length, and of a fragment of another of double that size in linear dimen- 
sions, which of course must have been nineteen and a half inches long— 
the largest specimen hitherto known to have been found. 
Dr. Jackson stated that trilobites had been found in the lime- 
Stone at the mouth of St. Croix river. He then exhibited the 
following specimens of minerals and fossils, viz. 
Fossils from the limestone belonging to the red sandstone group 
of Machias, Maine. A new mineral from Unity, New Hamp- 
shire, which he has analyzed and proposes to describe under the 
name of chlorophyllite; it was remarkable as containing a large 
amount of phosphoric acid. A new mineral from Natick, Rhode 
Island, described by him under the name of Masonite. ‘Tin ore 
from Jackson, New Hampshire, near the celebrated gorge of the 
White mountains. Phosphuret of copper and iron mixed with 
Vol. xx1, No. 1.—April-June, 1841. 21 
