164 THE CAMBRIAN AXD ORDOVICIAN DEPOSITS or MARYLAND 



be more correct. Stratigraphic evidence also shows that the Siimites 

 bed follows a considerable interruption of deposition, since the thickness 

 of strata between it and the Nidulites bed of the Chambersburg is most 

 variable. 



The best localities for obtaining collections of the Sinuites fauna are 

 just north of the Mason-Dixon line in southern Pennsylvania. East of 

 the Martinsburg shale belt in this region the following fossils have been 

 found : 



Fauna of Basal Martinsburg Shale (Sinuites Bed), Chambersburg 



Quadrangle 



Lingula riciniformis Hall 

 Leptobolus ovalis n. sp. 

 Conotreta rusti Walcott 

 Strophomena sculpturata n. sp. 

 Dalmanella testudinaria (Dalman) var. 

 Microceras inornatum Hall 

 Sinuites cancellatus Hall 

 Sinuites granistriatus Ulrich 

 Cyclora minuta Hall 

 Cyclora parvula (Hall) 

 Cyclora hoffmani Miller 

 Coleolus iowensis James 

 Conularia trentonensis Hall 

 Orthoceras junceum Hall 

 Trocholites ammonius Conrad 

 Eoharpes ottawaensis (Billings) 

 Cryptolithus tesselatus Green 

 Triarthrus flscheri Billings 

 Triarthrus ftecfci Green 

 Bumastus trentonensis Emmons 

 Proetus latimarginatus Weller 

 Cyphaspis matutina Ruedemann 

 Calymene senaria Conrad 



West of the shale belt in the Mercersburg quadrangle a larger number 

 of species has been identified in the Sinuites zone, but many of them are 

 identical with those in the more eastern belt of outcrop. 



