The Galena and Maqiioketa Series. — Sardeson. 181 
give the general results only of the investigation of the other 
two. After briefl}' reviewing them, a comparison of the same 
will be given in as far as they aid in determining the true 
relations and the relative time interval of the beds and for- 
mations of the Galena and Maqnoketa series. 
Orthis testudinaria. 
Orthis testudinaria auct. was found in part three of this 
paper to comprise several distinct species or varieties in the 
Ordovician. There is one of these viz. O. royota Sar. in the 
Galena series ranging from the top of the Stictopora bed ( num- 
ber 4 in ascending series) to the Lingulelasma bed (8). Of 
the Maquoketa speciies 0. eorpiUenta Sar. is found in the 
Triplecia bed (10) and the Leptaena bed (13), (>. iijnofd. Sar, 
is found inthj" Leptje.ia bed (13) only, so far as known; O. 
tersa Sar. belongs to the same or little later horrizon ; Orthis 
emacerata Hall ranges through three beds (12 to 14:),0.porrecta 
Sar. belongs to the Triplecia bed (10) but is found as a sec- 
ondarily deposited fossil in part of bed number 11 also, and 
O. fiUilis is known from beds number 10, and 13, Evidentlj^ 
O. emacerata Hall is not only contemporaneous but also of 
earlier occurrence in the lower beds at Cincinnati, Ohio, and 
in the Trenton Falls, N. York, series, while 0. corpulenta 
would seem to be early i-epresented at the latter locality. 
Plectambonites. 
Species of the genus PlerJantbonites in the Galena and Ma- 
quoketa series occur in geologic succession in tlie strata, but 
they do not form a corresponding morphologic series. Of the 
several forms that together comprise the Leptania [PlectaDibo- 
nites) sericea auct., of this region, no two occur in the same 
bed, but one of them is associated with /-". <jil)1)osa W. and S. 
P. gihijosa is not widely distributed, is narrow in range ver- 
tically, and it has no varieties. P. sericea Sow., as usually 
defined, is, on the contrary, one of the most widely distribu- 
ted of Ordovician brachiopoda here as in other parts of North 
America and in Europe, but it has several "varieties." at 
least five in this region, and these are each less widely' found 
and are all of more limited range, like P. ijiljliosa W. and S. 
It is not known how many kinds there are in the world, nor 
whether any of ours are found in p]urope, but it is evident 
that several kinds are found there, and the same varieties may 
