NO. 1395. 



CAMBRIA N BRA CHIORODA— WALCOTT. 



229 



The species may be o-r<>uped on surface characters into four sections 

 as follows: 



1. Costate: 



B. f appalachia. 

 B. coloradoensis. 

 B. dice. 

 B. exporreda. 

 B. hicksi. 

 B. lindstromi. 

 B. major. 

 B. obscura. 

 B. orientalis. 

 B. pumpeUyi. 

 B. 1'ichtJiofeni. 

 B. romingeri. 

 B. striata. 



2. Smooth costate: 



B. plicatella. 



3. Smooth striate: 



B. highlandi'usis. 



4. Smooth: 



B. f anomala. 

 B. harlanensis. 

 B. saffordi. 

 B. salemenm. 

 B. ivhitfieldi. 



Of the species referred to the genus, BiJl/7igsella exporreda is one 

 that departs from the t3^pical species in the absence of a convex delti- 

 dium; whether this is owing to the absence of a deltidium originally 

 or to its accidental removal from the specimens studied, is undecided. 



The species referred to Bllliiuj sella are: 



Name. 



Cambrian. 



Ord. 



i anomala, new species 



? appai:^^hia, new species , 



cn'.jradoensis Shumard 



dice, new species 



expm-recta 



exporrecta var. rugosicostata, new variety . 



harlanensis, ;iew species 



hicksi (Salter) Davidson 



highlandensis Walcott 



lindstromi Linnarsson , 



major, new species 



obscura, new species , 



orientalis Whitfield 



plicatella, new species 



pumpellyi, new species 



richthofeni, new species 



romingeri Barr. (Sp.) 



saffordi, new species 



saleme7isis Walcott 



striata, new species 



wMtfieldi Walcott 



Otusia, new subgenus of Billingsella. 



( Otusia) sandbergi Winchell 



