276 GEOLOGY OF ILLINOIS. 



fcwAf Hemipronites crenistria, Producing witulux, P. tenuicostatua, P.punct- 

 atus, Zaphrentes spinulosa, and numerous Bryozoans. 



Four miles south-east of Waterloo, there are .some old quarries known 

 as the "Portland quarries," which are in an earthy, buff-colored niagne- 

 sian limestone, of which only about six feet in thickness is exposed. This 

 rock closely resembles the limestone used at the cement mills north of 

 Columbia, in the edge of St. Clair county, and probably belongs to the 

 same geological horizon, near the base of the Warsaw division of the St. 

 Louis group. The rock exposed here has every appearance of a good 

 hydraulic limestone, and will probably prove to be valuable for the 

 manufacture of hydraulic lime. As no other beds were exposed in con- 

 nection with this, its stratigraphical position is only inferred from the 

 lithological resemblance of the rock to that used at the cement mill 

 above referred to; but I have little doubt it will prove identical with 

 that, as the exposure is nearly on the line of the antic-lined, axis already 

 mentioned as extending from a little east of Columbia to Waterloo, and 

 which must pass in its further extension very near to this locality. 



The Warsaw division of the St. Louis group is well exposed in the vi- 

 cinity of Columbia, w r here it outcrops on the hill sides east of the town, 

 and quarries have been opened in it at several points. It consists of 

 buff, brown and light-gray limestones, partly thin-bedded and marly and 

 partlj 7 massive ; the thin-bedded layers being tilled with Bryozoans and 

 the small Bracliiopoda peculiar to this horizon. The old quarries to the 

 left of the Centerville road were partly opened in the marly layers of this 

 rock, and the weathered debris afforded many fine specimens of its pecu- 

 liar organic forms. We found the Pentremites conoides quite common, 

 and were so fortunate as to find a single perfect specimen of P. oblhj_ua- 

 tus of Roam er, a very rare species in this State. RhynchoneUa mutata 

 and Ortliis dubia were also quite abundant at this locality. Mr. H. F. 

 HEKCEXER found, in one of these old quarries, a crushed specimen of 

 Melonites, that closely resembles the M. multipora of the upper division of 

 this group. 



Above the beds from which these fossils were obtained there is about 

 twenty feet in thickness of massive light-gray limestone, which stands 

 exposure well in the quarry, is free from silicious matter, and splits 

 evenly, and will afford an excellent building stone. This portion of the 

 bed is nearly destitute of fossils, but from some earthy layers above it 

 we obtained some fine specimens of Prod net us omttts. In the river bluffs, 

 these buff limestones outcrop in the vicinity of Eagle Cliff; also about a 

 mile and a half below Salt Lick Point, where they form a bluff about one 

 hundred and twenty-five feet in hight, the whole of which consists of 

 regular-bedded buff and light-gray limestones, that belong to this lower 



