The Galena and JIaqiioketa Series. — Sardeson. 25 
ignated forinations, and the latter are, further, onl}' the de- 
marcations between beds wliieh are more constant than others. 
The beds, which are the smallest divisions that it has been 
found practicable to designate, are not merely subdivisions of 
the formations and series, but are themselves nearly co-ordi- 
nate units of the entire succession of deposits, that are com- 
posed in the tive formations, or two series. And if a detailed 
description of the parts of the entire succession is to be given, 
the beds have each to be described in preference to the forma- 
tions. In truth the correlation and delimitation of forma- 
tional divisions have been practicable mainly through the 
knowledge obtained from a stud}' of the subdivisions. 
The}' form a more or less interrupted series of deposits that 
are predominatingly transitional, the one to the other, but in 
part alternatingly follow one another. Regarding the single 
beds, they may be uniform from bottom to top, or composed 
of transitional series of strata or of alternating ones, they 
ma}' be strikingly' uniform in characters throughout the en- 
tire area, as for example, the dolomitic limestone at the base 
and the one at the top of the Galena series, or their sedimen- 
tary and to a less or greater degree the faunal characters 
change gradually between localities. The beds varj' alike or 
unlike from place to place. Here and there the existence of 
any lithologic division remains doubtful, and if at the same 
place faunal evidence also fails a demarcation is locally im- 
practicable. Particularly where the alterations have obtained 
that produced the typical Galena limestone phase, much dif- 
ficulty is experienced. 
No one bed is faun ally distinct from the next one, but is 
distinguishable by some peculiar association of fossils. Some 
beds have one or more abundant species that are peculiar to 
it, others are characterized by the association of two or more, 
as for example the brachiopods. Orf.hi's subcequatci Con., which 
ranges from beds one to five inclusive, 'rtnd Rhynchouella i/ii- 
crebescen.s Hall, sensu stricto, which ranges from five to eight 
inclusive, are associated onl}' in bed number five. Besides 
data derived in that way from the distribution of sjDecies, 
others are to be taken from the minute evolutionary changes 
of species. The writer has been fond of using data of the 
latter class, but it will not be practicable to give them in con- 
