310 GEOLOGY OF ILLINOIS. 



equivalent. It contains numerous fossils, among which are Productus 

 costatus, P. Nebrascensis, P. Prattemanus, Spirifer cameratus, Atkyris sub- 

 tilita, Terebratula lovidens, Pinna per-acuta and M'yulina amplaf The 

 limestone No. 7 of the foregoing section is not fully exposed, but the 

 upper layers outcrop in the bed of the creek just above the railroad 

 bridge in pebbly layers, not unlike the upper layers of No. 2 as they 

 appear above the bridge on the main road north of Virdeu. This out- 

 crop is very similar in appearance to the upper layers of the Carlinville 

 limestone just below Corr's mill, on Macoupin creek, north-east of Carlin- 

 ville, and I have no doubt but this limestone on Sugar creek is the 

 equivalent of that. Below the railroad bridge, the shales underlaying 

 these limestones are the only beds exposed for some distance, but east 

 of Auburn the limestones are again met with, and are found in occa- 

 sional outcrops from this point to Crow's mill, seven miles south of 

 Springfield, where the rock for the old State House was obtained. At 

 Peddicord's quarries on Sugar creek the State House rock is well ex- 

 posed, aifordiug the following section : 



No. 1. Thin bedded ferruginous limestone 2 to 3 feet. 



No. 2. Massive coarse-grained limestone 4 " 



No. 3. Clay shale partly bituminous 6 " 



No. 4. Thin bedded limestone 3 to 4 " 



No. 5, Sandy shale 10 to 12 " 



The material for the old State Hous was obtained mainly from No. 2 

 of the foregoing section, and there is a nearly continuous outcrop of 

 these beds from this point to Crow's mill two miles below, where the old 

 State House quarries were located. This rock is a coarse-grained brown- 

 ish-gray criuoidal limestone, almost entirely composed of criuoidal 

 joints and the calcareous remains of marine mollusca, cemented together 

 by calcareous and ferruginous sediment. In addition to the fossils 

 already enumerated as occurring in this limestone at the locality north 

 of Virdeu, the quarries here afforded numerous specimens of Syringopora 

 multattenuata. which seems to belong in the clay shale under the lime- 

 stone No. 2 'of the foregoing section, and so far as I am aware has been 

 found nowhere else but in this shale in Sangamon and Macoupin coun- 

 ties. Some of the masses obtained on Sugar creek are nearly a foot in 

 diameter. This limestone has also afforded fine specimens of Cladodus 

 mortifer, Petalodus destructor, and Cyathocrinus Sangamonensis. This 

 rock possesses the same lithological characters, and affords exactly the 

 same group of fossils as the upper division of the main limestone at 

 LaSalle, and I have no doubt they are stratigraphical equivalents. Below 

 Crow's mill to the outlet of Sugar ere; k into the Sangamon river, the 

 sandy shales and sandstones intervening between this limestone and 

 the little coal outcropping at Howlett, are the only beds to be seen. 



