PALAEONTOLOGY OF NEW-YORK. 
with certain shaly beds in the Potsdam sandstone, or even perhaps at the 
base of this formation*. 
* The rediscovery of this trilobite in an authentic locality, after a lapse of so many years, is extremely 
interesting. The Paradoxides harlani was described by Dr. Green in the Supplement to his Monograph 
in 1835, from a specimen belonging to the Cabinet of Francis Alger, esquire, and believed to be from 
an undoubted American locality. Since no other specimens have been seen, some doubt had arisen as to 
the American origin of the one in question; and since the original has been lost, no other representations 
of it remained except the cast of Prof. Green. The specimens now obtained from Braintree are imbedded 
in a rock of precisely the character of the original specimen obtained from Mr. Alger, which the writer 
well remembers seeing in the possession of Dr. Green. 
During this interval, fragments of trilobites have been several times found upon George’s island in 
Massachusetts bay, but they do not appear to have attracted the attention of the naturalists of the vicinity. 
The history of the present discovery appears to have been as follows : 
“ About five years ago, Mr. Eliphas Hayward first observed these fossils on opening his stone quarry 
for the purpose of obtaining underpinning and ballast stones. Without knowing their nature, he still looked 
upon them as interesting curiosities, and laid aside the specimens which have lately been brought before 
this Society. 
“ He showed them to Peter Wainwright, esquire, of Boston ( Mass.), who at once recognized them 
as trilobites, and brought them to Boston for the inspection of geologists, and presented two specimens 
to our associate Prof. William B. Rogers, to whom the Society is indebted for the first notice of these 
remarkable fossils, so important in the determination of our geognostic horizon. 
“ A few days after Prof. Rogers’s visit to the quarry, Dr. Jackson, by invitation of Mr. Wainwright, 
visited it and made a minute examination of all the geological phenomena which it presents, and obtained 
specimens of the trilobites through the kindness of Mr. Hayward, and by search at the quarry in company 
with Mr. Wainwright. Two specimens were obtained; one entire, which is 8% inches long and 4 inches 
wide. The other, of which only the head and half the body was obtained, is 6 inches wide, and its hood is 
7.1 inches across by the base of the head : hence the length of this specimen must have been 12 £ inches at 
least, which is about the size of the largest specimens of the Paradoxides tessini discovered in Sweden. 
The smaller individual has 21 articulations, but none in the tail beyond the lateral appendages, and in this 
respect differs from the P. tessini, its nearest analogue, which has, according to Brongniart, four faintly 
marked depressions or folds crossing the tail transversely. They may have been obliterated in our specimen 
by the changes the rock has undergone. 
“ These trilobites of Braintree occur in a blue gray argillaceous slate, containing silicate of lime, but no 
carbonate, and some disseminated iron pyrites. The stratification of the rock, as indicated by its grain and 
cleavages, dips to the north 50 degrees, and runs east and west. It is but slightly altered by heat in thoso 
portions where the trilobites are found; but near the sienite rocks, it is filled with nodules of epidote, and 
closely resembles the altered slates of Nahant. There is a small vein of quartz, bearing iron pyrites in it, 
which cuts through the slate strata at right angles. There are also slickensides surfaces on some of the 
cleavages or joints in the quarry; indicating, as it is supposed, the polishing effects of rapid earthquake 
movements at the period of disturbance of the strata at the time of their disruption by intruded sienite. 
“ These are all the marks discoverable of metamorphic action of igneous rocks on these sedimentary 
strata, though the slate rocks are hemmed in by the sienite rocks on both sides, and the belt of slate is 
quite narrow*.” 
A notice of this discovery has likewise been published in the American Journal of Science and Arts for 
September 1856, by Prof. W. B. Rogers, who also read a notice of the same before the American Associa¬ 
tion for the Advancement of Science. 
* Extract from a Report made to the Eoston Society of Natural History by Dr. C. T. Jackson. 
