no. 1646. REVISION OF BEYRICHHDJE—ULRICH AND BASSLER. 299 



at the same time completely disassociating it from its most obvious 

 alliance, it is provisionally suggested that the Li'i"<>n l> be distinguished 

 merely subgenerically from Beyrichia, and that it be known by the 

 proposed name Steusloffia, with Beyrichia linnarssoni as the type. 



GROUP OF B. [NTERRUPTA. 



Another resemblance that has Led to unnatural associations is that 

 borne to Bollia by a small group comprising Beyrichia granulifera, 

 new name (Bollia granulosa Krause, specific name preoccupied under 

 Beyrichia), and B. v-scripta (Krause), two Ordovician species, B. 

 damesi Krause, and B. interrupta (Jones and IIoll), two Silurian 

 species. In fact, with the exception of B. (honest, all of these species 

 were originally referred to Bollia. but, as will be clear enough when 



Pigs. 47-51. — 47. Right valve of Beyrichia interrupta (Jones), x 20. 48. Left 

 valve op Beyrichia v-scripta (Krause), x 15. 49. Right valve op Eurychilina 

 subradiata tjlrich, x 20. 50. i. kit valve op beyrichia clavata kolmodin. 51. 

 Left valve of Beyrichia (Steusloffia) acuta (Krause). (Fig 17 is after Jones, 

 is after Krause, 19 after Ulrich, 50 after Kiesow, and 51 after Krause.) The 

 illustrations show possible derivation in.- the Beyrichia interrupta group 

 from Eurychilina and its relations to the Beyrichia clavata group and t<> 

 Steusloffia. 



that genus is considered, they do not belong there. The curved ridge 

 in these species seems really to have no greater taxonomic significance 

 than the similar node and ridge often seen in typical Eurychilina. 

 On the other hand, the lobation of their valves, though in part ob- 

 scure, is essentially that of Beyrichia, the connection with species of 

 this genus like B. Jones', and B. clavata being, apparently at least, 

 very clear. 



The group suggests passage from Primitiidse to Beyrichia, but 

 whether this sui>-o-estion is based on fact or is merely apparent and 

 thus misleading, can not be decided with the evidence at hand. How- 

 ever, the possibility of species conforming to the generic diagnosis of 



