REVIEiVS III 



The Bellefonte, Pa., Section of the Ordovicia?i. By George I.. 

 Collie. 



The section described is located at Bellefonte, Pa., the geographi- 

 cal center of the state. It lies in the Nittany valley, a denuded anti- 

 cline, between the isoclinal Bald Eagle ridge on the northwest and the 

 synclinal Nittany ridge on the southeast. 



The rocks dip to the northwest, the dip varying from 8 ° at the 

 crest of the anticline to So ° and 90 ° at the top of the section in Bald 

 Eagle ridge. The total thickness of rocks in the section is 6,000 feet, 

 of which 5,000 feet are limestones and 1,000 feet shales. The litho- 

 logical features of the rocks have been described in detail in the 

 various geological reports of the state, and do not need further descrip- 

 tion. Little attention has been given to the faunas found in the 

 rocks, and this paper aims in a measure to supply this deficiency. 



Four fossiliferous horizons have been recognized in the Jimestones 

 and two in the shales. The lowest horizon (A' of the paper) is 345 

 feet above the base of the section. It occurs in an oolitic limestone 

 and is but a few inches in thickness. Ophiletas are the most abundant 

 types found, though Murchisonias occur sparingly. The Ophiletas 

 are related chiefly to O. Complanaia. This indicates the Calciferous 

 age of this horizon. 



Between this lowest horizon and the next succeeding horizon (A"") 

 there are 600 feet of unfossiliferous rocks. Horizon A"" contains a 

 mixed fauna. Its relationships are in part with the Calciferous, in 

 part with the Quebec, and in part with the Chazy. The most abun- 

 dant fossil is Asaphus Marginalis, a Chazy form in New York. 

 Various species of Ecculiompholus occur, all of which are closely 

 related to forms described by Billings from the Quebec of Canada. 

 Ribenia Calcifera and Ophileta Uniangulaia, typical Calciferous fossils, 

 are found also. Provisionally this horizon is referred to the Calcif- 

 erous. Above A^ are 1,200 feet of unfossiliferous rocks before the 

 third horizon A^ is reached. 



Horizon A^ is characterized by an overlapping of faunas. Strati- 

 graphically speaking, the horizon is Chazy, but it contains few Chazy 

 fossils. The relationships of the fauna are with Canadian and New- 

 foundland types rather than with those of the interior as represented 

 in New York. The most interesting fossil found is Botliyurus ainpli- 

 fnarginatus, a form described by Billings from the Calciferous of the 

 Mingon Islands, Gulf of the St. Lawrence. Maclutia Ma^na, M. 

 Affinis, M. Acuminata are common. The mention of these names 



