rANHisE]        ISOLATED    AREAS    OF    THE    MISSISSIPPI    VALLEY.  271 
21  Based  on  unpublished  field  notes  made  by  Profs.  Raphael  Purapelly  and  C.  R. 
V^an  Hise,  in  the  summer  of  1890. 
22  Contributions  to  the  Geology  of  Texas,  Dr.  Ferdinand  Roemer.  Am.  Jour.  Sci., 
id  ser.,  vol.  vi,  1848,  pp.  21-29.  See  also  Texas,  etc.,  Dr.  Ferdinand  Roemer,  1849, 
)p.  464,  with  a  map. 
as  Letter,  B.  F.  Shumard.     Trans.  Acad,  of  Sci.  of  St.  Louis,  vol.  I,  1860,  pp.  672-673. 
24  The  Primordial  Zone  of  Texas,  with  descriptions  of  New  Fossils,  B.  F.  Shumard. 
tan.  Jour.  Sci.,  2d  ser.,  vol.  xxxn,  1861,  pp.  213-221. 
25  A  Preliminary  Report  of  the  Geological  and  Agricultural  Survey  of  Texas,  S.  B. 
Buckley.     Austin,  1866,  pp.  81,  4. 
26 First  Annual  Report  of  the  Geological  and  Agricultural  Survey  of  Texas,  S.  B. 
3uekley.     Houston,  1874,  pp.  142. 
27  Second  Annual  Report  of  the  Geological  and  Agricultural  Survey  of  Texas,  S.  B. 
Buckley.     Houston,  1876,  pp.  96. 
28  Note  on  the  Paleozoic  Rocks  of  Central  Texas,  Charles  D.  Walcott.  Am.  Jour, 
sci.,  3d  ser.,  vol.  xxvin,  pp.  431-433. 
29  A  Partial  Report  on  the  Geology  of  Western  Texas,  Prof.  Geo.  G.  Shumard.  Aus- 
in,  1886,  pp.  145. 
30 A  Preliminary  Report  on  the  Geology  of  the  State  of  Texas,  John  W.Glenn, 
^irst  Annual  Report  of  the  Geological  Survey  of  Texas,  1889,  E.  T.  Dunible,  State 
geologist,  pp.  245-246. 
:il  Preliminary  Report  on  the  Geology  of  the  Central  Mineral  Region  of  Texas,  Theo. 
5.  Comstock.     Ibid.,  pp.  239-391. 
33  Report  on  the  Geology  and  Mineral  Resources  of  the  Central  Mineral  Region  of 
Pexas,  Theo.  B.  Comstock.     Second  Ann.  Rept.  Geol.  Survey  of  Texas,  1890,  E.  T. 
