. a oy ‘Wisconsin’ and part of I Tales: "ee + Ke 
Otani to tlie: genera tiiiedbus, Trinucleus, and Triarthrus, Foes Pl: 
_ %, Fig. 4,) and probably ‘belonging to more than one species; one !.. °° 
~~ of which seems to have been provided with spines, at least two “4 
= “inches-in length, curved at the extremity into th® form of a bar- 
‘bed fish hook... Fig. 5, Pl. 7, represents one of these, found by © 
. C. Macy near the mouth of Miniskah.”. 
Speak ing of the distinction between the /ower and upper mag- 
esian. limestone formations of the Upper Mississippi, Dr. Owen ,.- 
remarks, page 
“The tyavel ler who has visited the Upper Mississippi canno ot 
fail to have remarked the peculiar outline of hill that bounds the 
prospect on either side of this picturesque portion of that majes- 
tic river.» Het must especiall y have noticed the conspicuous per- 
pendicular. walls of rock, that rise from out the grassy slope, or 
green: ‘copse w ood, in massive cliffs, and terrace the heights as 
' with: drtatrapted natural battlements from the Maquoketa river to 
ss: ‘Lake. ea It is not, however, until the geology of the noe 
has be nr Closely inspected, that he is able to discover that t 
vills which present themselves to view below Turkey river do ni 
: ~ belong to the same geological era as those which appear above the 
_ © Month of that stream. Nay, so uniform are they in their general 
aspect, that the miner himself, who has spent the best part of his 
ys in excavating and exploring their recesses, is wont to regard 
them as identical. So they are, looking only to their chemical com- 
position. Both are limestones, highly magnesian,* in heavy beds, 
of great compactness and durability ; but ‘they are separated from 
other by from one hundred and fifty to two hundred feet of 
other strata, the upper hundred feet of which teem with peculiar 
races of fossil forms, constituting a distinct geological epoch, and 
marking a long lapse of time that has intervened between the pe- 
riod of deposition of these limestones. In my former report I 
= gt designated them the “lower” and,‘ upper” magnesian lime- 
of Wecaels: and Towa. This distinction, as will appear 
tsof magnesian limestone, south 
Turkey river, are composed of the upper of these formations, : 
; all those north of Wisconsin river, as w for as Lake Pepin, 
he are of the lower. 
“Ani 
