TRENTON LIMESTONE. 
67 
I have devoted a considerable space to the illustration of this species, and my only 
apology must be, that since the work will be mainly distributed among learners, I desire 
to make it readily understood by them. If therefore the author’s own labors can in any 
manner be offered as a substitute, the student may find his task easier than to be left in 
such cases with a single illustration, while many hours of labor might be required to 
convince himself that all these forms were identical. 
Position and locality. This species occurs in infinite numbers in the Trenton limestone, 
and in nearly every part of the rock. In some localities the hemispheric, and in others the 
cylindrical and ramose forms prevail, and not unfrequently both occur together. 
This species commences its existence soon after the final deposition of the Calciferous 
sandstone, where it is somewhat rare. In the Trenton limestone it presents its maximum 
development, but is still quite common in the Hudson-river group. At the west it is equally 
abundant and protean in its forms in both these groups, acquiring its maximum development 
at a higher point, geologically, than in New-York. The same species apparently reappears 
after the deposition of the Oneida conglomerate, and is found in the Niagara group, as 
well as in the Pentamerus and subsequent limestones. A similar, if not identical species, 
occurs in the Hamilton and Chemung groups. 
Its geographical range is equally extensive with its geological range. It occurs in nearly 
every part of New-York, in many places in Pennsylvania, in Virginia, Kentucky, Ten¬ 
nessee, Ohio, Indiana, Michigan and Wisconsin, as well as Canada. 
Its principal localities in the Trenton limestone, are Trenton Falls, Middleville, Jackson- 
burgh, Watertown, Lowville, Turin, Plattsburgh, Cliazy, Glen’s Falls, and numerous 
other localities in the Mohawk, Champlain and Black River valleys. {State Collection.) 
102. 3. CHiETETES I RUGOSUS ( n. sp.). 
Pl. XXIV. Figs. 2 a, b. 
A polymorphous or ramose coral ; branches somewhat compressed ; tubes radiating 
almost vertically from a central axis ; diaphragms numerous, regular ; interior walls of the 
tubes rugose, or transversely wrinkled. 
The tubes are larger, the interior distinctly rugose, and otherwise presenting a somewhat 
different aspect from the preceding, to which, however, it is closely allied. The specimen 
figured shows a ramose form, the branches diverging in three directions, but they have 
been broken off before the coral was imbedded. 
Fig. 2 a. The specimen of the natural size. 
Fig. 2 b. An enlarged portion, showing the form of the tubes and the rugose interior. 
Position and locality. In the lower part of the Trenton limestone, at Middleville, Herki¬ 
mer county. 
