No. 275.] 
289 
characters; for though without doubt erery group embraces its peculiar 
fossils, yet in all localities these may not be so marked as to excite at- 
tention, and in some may possibly be absent. It thus becomes a desi- 
deratum to distinguish rocks by names which cannot be traduced, and 
which, when the attendant circumstances are fully understood, will ne- 
ver prove fallacious. The basis of this nomenclature is derived from 
localities; and the rock or group will receive its name from the place 
where it is best developed. For example, the rock denominated in the 
section calcareous shale, simply to distinguish it from the green argillace- 
ous shales below, will be called Rochester shale. In lithological cha- 
racters it is extremely like one far higher in the series, but the fossil 
contents are entirely different. This contains the Asaphus caudatus, 
Trimerus delphinocephalus, Platynotus Boltoni, besides species of Or- 
this and Delthyris, all peculiar to this rock, and the characters if studied 
and well understood at Rochester, will guide the observer in all subse- 
quent examinations. The limestone at Lockport excavated for the pas- 
sage of the canal, we propose to call Lockport limestone. At this 
place the rock possesses in an eminent degree the geodiferous charac- 
ter, which has hitherto given it its name; but this is quite inapplica- 
ble to the same rock where seen in Wayne county. Yet it is be- 
lieved that if thoroughly examined in all its varieties at Lockport, it 
will not be mistaken even in its eastern prolongation where it becomes 
a dark, nearly black, compact limestone. At some intermediate points, 
as Rochester, the rock exhibits an intermediate character, and at such 
places it can be advantageously studied. The rocks just named, toge- 
ther with the green shale and iron ore, the upper member of the series 
being the Lockport limestone, belong to a group very appropriately 
termed by Mr. Vaunxem, Protean. To this belongs a rock which has 
been designated by its contained fossils. Associated with the green 
shale and iron ore is a mass of limestone characterized, as Mr. Conrad 
observes, by broken shells of Pentamera, which abound in this rock and 
are found in none other in the district. 
It may be objected to the proposed nomenclature, that in order to 
become familiar with the rocks, they must be examined at the designa- 
ted localities. It is true that this system requires more labor than the 
study of a few cabinet specimens; which we are sometimes told is suffi- 
cient to prove, at sight, every rock on the globe. But thus we shall be 
enabled to avoid the egregious errors which have led to such false im- 
pressions regarding the identity of rocks; and if this system be estab- 
lished, and means taken to ascertain the character of strata, the commu- 
nity may be saved the useless expenditure of many thousands in search- 
[Assem. No. 275.] 37 
