dinary size and perfection. So abundant is it that a dozen indi- 
viduals may sometimes be seen in thé space of a few feet. The 
species is quite different from the one in the Keokuk beds, be- 
ing More robust and the volutions of the spiral axis less rapidly 
ascending, 
This second Archimedes limestone seems not to have been re- 
Cognized in the section of Dr. Owen; and judging from localities 
cited, it appears to have been confounded with the lower Ar- 
chimedes or Keokuk limestone. The position however of the 
arsaw Archimedes limestone is above the geode bed, the Ar- 
chimedes is a distinct species and it is associated with several spe- 
ft of crinoids, fish teeth, etc., which do not occur in the lower 
s, 
_ The arenaceous bed which terminates this group, and which 
likewise contains Archimedes and joints of crinoidal columns, is 
Succ dbya light gray, compact limestone, which is often con- 
cretionary or brecciated in its structure. Its most conspicuous 
Ossil in many localities is Lithostrotion floriforme. : 
_ this limestone is terme r, Owen the “concretionar 
limestone,” and by Prof, Swallow the “St. Louis limestone.” 
It is the same rock which forms the low cliff be ow Keok 
3 
Alton, Ill; the limestone of St. Louis in whole or in part; the 
limestone of St. Genevieve; the limestone of Prairie du Rocher, 
am ; ooh in part, the bluffs bordering the American Bottom, be- 
Ww ton, Tl. 7 io aaa i 
At this point the sections both of Dr. Owen and Prof. Swal- 
Cease, so far as limestones are designated. ‘The Concretion- 
* 
After a careful examination of the locality cited by Dr. Owen, Tam unable to. 
find a second Seas Hina sai ¢ h it is not difficult to see how such an 
ogee near the mouth of the Des- 
error should oe 
han: ent Soon in measuring the section 
a oe 
