Geological Survey of the State of New York. 99 
in deference to the opinion of that author. The first of these 
synonyms (derived from d«z70:) stands in the place of Producta or 
Productus, a name to which grammarians have objected. 
“The second genus, Aérypa, (from « privative, and tgvza,) is 
divided from Spirifer, and includes those species which have a 
short hinge line without a large area, and are either destitute of a 
foramen, or possess only a small triangular one. ‘They are round- 
ed shells, and are not furrowed like the typical species of Spirifer ; 
the internal spiral arms are preserved in some species. Atrypa 
affinis, and similar striated shells, would form another natural 
group, in which the internal structure, as well as the general 
form, is different ; for the spiral appendages, if ever they possess- 
ed any, do not appear to remain; and there are two short cre- 
nated teeth in the hinge. The species of this division have gene- 
rally been described as T'erebratule by British authors, but they 
have acute, not perforated beaks. 
“The genus Orthis (og0o;) is another division of Spirifer, no 
species of which has heretofore been described in England; it is 
distinguished from Spirifer by the long narrow hinge and circular 
flat form of the striated shells. ~ 
“Our genus Pentamerus is called Delthyris by the Swedes, 
but we see no reason for altering the name. If we were well 
assured of the stability of the genus Delthyris, we should remove 
to it Atrypa galeata, and perhaps one or two other species of 
Atrypa.”’ 
In the survey of the first district, the trap region of Rockland Co. 
is described as forming a narrow belt, the Palisades, along the 
Hudson River, from the N. Jersey line to near Haverstraw, thence 
it ranges off to the northwest, then west, and finally’ south west, 
near the base of the Highlands, and disappears. A branch of it 
strikes off westerly, about two miles north of Nyack, towards 
the Highlands. ‘These ranges are from a quarter to two miles 
broad, and on the east and north present mural columnar e 
ments from three to eight hundred feet high, with the usual ie 
bris at the base ; and the south and west sides usually slope off 
more gradually. The sandstone beneath is cut through by large 
and small dikes, and its layers are separated by lateral intrusions 
of trap. The trap varies from coarse crystalline to.very compact 
greenstone, and from slaty clinkstone to a coarse amygdaloid. 
The sandstone presents a great variety of color, and of aggrega- 
