26 



SMITHSOXIAX MISCELLAXEOUS COLLECTIOXS 



VOL. 70 



sedimentar}- rocks of the re,i;'ion were massive, unfossiliferous lime- 

 stone prolxibly of I 're-Cambrian age. with a great erosional uncon- 

 formity at their toj). Immediately following this unconformity is 

 an arenaceous limestone several feet thick containing the Coryncx- 

 ochiis fauna hitherto believed to be of Middle Cambrian age. h'ol- 

 lowing this bed. in apparently normal succession, are the well-known 

 Lower Cambrian shales containing OlcncUits and other trilobites. 

 In hgure 25 the point of contact between the two Lower Caml)rian 

 formations is indicated at C. Collections of two faunas of Lower 

 Cambrian age were secured during these studies. 



Fig. 26. — Open iron ore pit at Cornwall. Pa. riiulut;raph Ijy Resser. 



Dr. Resser also spent some days in collecting mineral specimens 

 from the celebrated ore banks at Cornwall, I'ennsylvania. a locality 

 famous for its well-ijreserved minerals, but unfortunateh' poorly 

 re])resented in the Museum collections. These ore banks are in the 

 hills between Lancaster and Lebanon counties and. as they have been 

 worked since 1853. they are now great o])en ])its from which the 

 minerals can be obtained. The ore is the iron oxide magnetite, 

 formed along the lines of contact of an igneous mass intruded into 

 Paleozoic limestone. The magnetite often occurs well crystallized. 

 but the mineralogical interest of the locality lies in the minerals of 

 copper, iron, and magnesium silicates which were formed with the 

 magnetite. The photograph (fig. 26) shows the arrangement of 



