TRENTON LIMESTONE. 
47 
by side. It is equally abundant at Frankfort, Kentucky, where it received the name of 
Trianisites cliff or dii. 
No. 1. The Giant isotelus (Isotelus gigas), size reduced one-third. This trilobite, the 
original of which is in the collection of the State, was found at Middleville. Fragments are 
numerous in almost all the localities of this limestone. More have been noticed at Fort-Plain, 
than at any otMr place. The range of this species is about the same as that of the Favosite. 
The other fossils, which are abundant, and by association characteristic of this limestone, 
are the following : 
Open bellerophon (Bellerophon apertus), has the same lower range as the latter named 
fossils, but reappears in the sandstone shale of Pulaski, should the species be the same, 
which is not the opinion of Dr. Emmons. 
Semioval strophomena (Strophomena semiovalis), is an exceedingly abundant fossil in the 
Trenton limestone, and has the same range with the preceding ones. 
Alternate strophomena (Strophomena alternata), is in like number, with the same range. 
Tortoise orthis, or Orthis testudinaria (Tortoise-shaped, orthis), is in prodigious numbers, 
and occurs also in the sandstone shale of Pulaski, and likewise, but sparingly however, in the 
Water-limestone group, unless mistaken for a cognate species. Considerable difficulty, in 
fact, exists with this species ; the individuals being in such profusion, that great attention is 
requisite to separate the incidental from the constant character. 
Among the many fossils which also occur in this limestone, but are not so numerous as 
individuals, a few only will be mentioned. 
The genus Delthyris commences in this rock, but the number of individuals in the third 
district is not great. In Ohio and Kentucky, this limestone is prolific of this genus. There 
are three or more different species in the district; the common one is the Little-ear delthyris, 
(D. microptera.) 
Of orthocerae, there are several in this rock, one of which has been found over four feet in 
length, not yet named. At Trenton falls, fragments of these large ones maybe seen between 
the bridge and the mill-dam at the south or lower end of the gorge or excavation. The most 
characteristic ortlioceras of the rock is the Striated, (Orthoceras striatum.) It is found in 
many localities, but more numerous at Trenton falls, towards the lower part of the mass. 
The O. duplex of Mr. Conrad also occurs, but it is very rare ; the genus Actinoceras, to 
which it belongs, being rather confined to the mass intermediate to the birdseye and this 
rock. 
Of the curved chambered shells, there are several: the most common is the Trocholites 
ammonius of Mr. Conrad, which is very numerous, but in one layer only, and in two localities 
as yet observed; namely, near Newport,- and by the side of the creek between Middleville 
and Fairfield academy. This genus is as yet confined to this rock, and to the lower rocks of 
Salmon river, the Pulaski sandstone. The Phragmolites compressus of the same author, is 
also confined to this rock, but is extremely rare. • In the collection at Trenton falls, there 
was a species of Cyrtoceras, about six inches in diameter, said to have been taken out of this 
