6o THE JOURNAL OF GEOLOGY. 



beds appear to have come from a single one of those subdivis- 

 ions, one quite above the rocks of Newark, and the same that 

 contains the Richmond coal. That coal, Gilbert says, does not 

 occur in New Jersey, meaning, perhaps, not in large deposits 

 like the Virginian ; but yet no doubt it occurs there in thin lay- 

 ers and traces, just as in Pennsylvania, since the same subdivis- 

 ion of rock beds does extend into New Jersey. It is, perhaps, 

 uncertain whether the Newark rocks, with their two reported 

 fossil species, belong even to the Mesozoic. 



There is in eastern Pennsylvania and New Jersev great 

 unconformity at the top and bottom of the rocks in question ; 

 but it is not yet so certain that beds of the same age as the low- 

 est of them do not occur conformable to Paleozoic beds in west- 

 ern Pennsylvania and elsewhere in eastern America, to say 

 nothing of the West. 



Clearly no claim for unity in the supposed group could be 

 based on geographical continuity. 



Would it not, indeed, be still more reasonable if he main- 

 tained that the Paleozoic rocks of the Appalachian region were 

 a stratigraphic integer or unit, and consequently deserved a sep- 

 arate name? 



2. There are, in truth, strong arguments in favor of gener- 

 ally giving local geographical names to stratigraphical groups, 

 whether large or small. Yet there are many names of a differ- 

 ent character that have had merit enough to become universally 

 accepted, such as Paleozoic, Mesozoic, the Old and New Red 

 Sandstones, Trias, Oolite, Calciferous, Corniferous, Saliferous, 

 Carboniferous, Coal Measures, Millstone grit. Cretaceous chalk. 

 Eocene and the like. Of course, the larger the group, the 

 less easy to find a suitable, well-characterizing local name, the 

 name of a place or region where the beds have been particu- 

 larly studied, or much seen of men, or, as a whole, finely dis- 

 played ; and that would be a difficulty with so extensive a set of 

 beds as the one in question. 



3. Gilbert, while insisting that Newark is the proper term in 

 the present case, evidently admits that some such geographical 



