SILURIAN FOSSILS 



65 



Fig. 106 



beak. Two species of Stegerhynchus are common in the 

 Niagaran. 



Anastrophia internascens is like Stegerhynchus but 

 is wider than long and has rounded beaks. It is common 

 in the Upper Niagaran. 



Fig. 107 



Uncinulus stricklandi is like the last 3 genera but has a globose 

 shell which is characteristic. It is common in the Cedarville. 



In Homoeospira , another shell of the same general appearance, 

 the shell is only moderately thick, not globose. It is common in the 

 Cedarville. 



Fig. 108 



Dolerorthis flabellites (called Orthis flabellites in older publi- 

 cations) has no sinus or fold (fig. 108) and is easily recognizable by 



its wide hinge line, rather flat valves, and strong costae. It is common in the Dayton, rare 

 in the Euphemia and Springfield. 



Fig.lOB 



Conchidium laqueatum (fig. 109) is a large brachiopod, 

 some specimens almost as large as Pentamerus laevis. Its 

 distinct ribs separate it easily from that species. C. laqueatum 

 is abundant in the Upper Niagaran. 



The genera Brachyprion , Fardenia "(fig. 110), Protomeg- 

 astrophia and Strophonella have more than 40 ribs on each 

 valve, a wide hinge line, no sinus and fold. In addition, the 

 hinge line has a number of small tooth -like projections, visi- 

 ble on single valves. They can be separated only on the basis 

 of internal characteristics. 



The remaining genera also have more than 40 radial ribs, 

 but they have a sinus and fold. The sinus and fold may be weak 

 but are always apparent. 



Fig. no 



