WHITE.] CARBONIFEROUS FOSSILS. eal 
be observed, too nearly with the description and figures of P. grayvillen- 
sis, as given by Norwood & Pratten, in the work aboye cited, to warrant 
their separation under a new specific name. The principal differences 
presented by these examples are the greater prominence of the band- 
bearing carina, the more distinct furrow separating the carina from the 
proximal portion of the volution, and the greater prominence of the re- 
volving lines which cover the surface. These differences, so far as they 
are observable upon our examples, seem not to be incompatible with 
specific identity. Jf these examples are specifically identical with P. 
grayvillensis, as they are believed to be, their discovery in Arizona adds 
another to the interesting facts already known, showing the wide geo- 
graphical distribution of Carboniferous species. 
