Recent detailed field mapping and a new understanding of the
   internal stratigraphy of the Road Canyon and Cutoff formations have
   provided the necessary framework to improve the biostratigraphic
   resolution of the Roadian Stage (early Guadalupian Series).  Shumard's
   (1 860) basal "black limestone" at the bottom of Guadalupe Pass was          
   explicitly included as the lowerrnost unit when Girty (1902) proposed        
   the Guadalupian Series. Adams et al. (1939) considered the black             
   limestone to represent the Bone Spring Limestone, and its fossils to be
   Leonardian.  Accurate correlation demonstrates that the black lime-
   stone is the upper unit of the basinal Cutoff Formation. The                 
   reassigmnent of previously described fossil localities to their correct      
   stratigraphic position clarifies temporal faunal relationships, and the
   Road Canyon and Cutoff formations are proven to be largely
   correlative. Roadian ammonoid, conodont, and fusulinid faunas are            
   distinctive, and the biostratigraphy records when each of these              
   important groups is first represented by characteristic Guadalupian          
   forms.  Predicated on both the improved database and consideration of
   priority and stability, a return to Girty's original Guadalupian Series
   concept is recommended.  This supports retaining the Roadian as the
   basal stage of the Guadalupian Series. It is also proposed that the             
   mutual basal boundary of the Guadalupian and Roadian be established
   within the morphological continuum through which the conodont                
   species Mesogondolella idahoensis evolved into M. nankingensis.             
   Thus defined, the Guadalupian Series is a leading candidate as the
   international standard for establishing a formal Middle Permian Series.