91 



The Austin limestone contains fossils such as Gryphcea vesicularis, 

 RadioUtes Austlnensis, Nautilus DeKmji ? , BacuUtes anceps, Hemiaster 

 perastatus, Corax heterodon^ Lamna Texana, which indicate a fauna of 

 the chalk group as well in Europe as America. I regard that sub- 

 division of Dr. Shumard as the youngest of all the cretaceous strata 

 of Texas as yet described ; and of the age of the white chalk or 

 Senonien of France. 



The indurated blue marl or Exogyra arietina marl^ which comes 

 next in Dr. Shumard's theoretical section, contains the Exogyra arie- 

 tina in profusion, and also the Gryphcea Pitclieri. The author says 

 " that it is well exposed towards the base of Mount Bonnell, near 

 Austin." Mount Bonnell is also cited as a typical locality for his 

 Comanche Peak group ; by giving a section of that mountain, Dr. 

 Shumard would have shown the Austin limestone placed according to 

 his views, but none is given. Dr. George G. Shumard found this 

 indurated blue marl resting upon the Washita limestone in the State 

 of Arkansas, and as the Washita limestone is another of the sub- 

 divisions not defined with sufficient exactness to serve as a term of 

 comparison, I am inclined to consider the indurated blue marl as a 

 subdivision in the middle of the Comanche Peak group, and above or 

 even included perhaps in what Dr. Shumard terms the Washita lime- 

 stone. 



The Washita limestone constitutes according to the author, an im- 

 portant member of the Texan cretaceous system ; its name is taken 

 from Fort Washita, where Dr. George G. Shumard found it finely de- 

 veloped. The first desiderata are, a good description, bed by bed, of 

 all the cretaceous strata of Fort Washita, with the distribution of the 

 fossils contained in them. This want is not supplied by the memoir 

 of Dr. Shumard ; the fossils are given in bulk, although it is more 

 than probable that in those 120 feet thickness of strata, there is a 

 regularity and order in the distribution and relative position of the 

 fossils ; they cannot all range from the bottom to the top. It is clear, 

 from the Hst of fossils, that the greater part of the Washita limestone 

 belongs to the lower cretaceous rocks of America, and is on a parallel 

 with the Neocomien of the Jura. Without a good drawing of the 

 Inoceramus prublematicus, and even without a description of the 

 fossil, so called by Dr. Shumard, I may be permitted to doubt its ex- 

 istence ; and, if it is found at Fort Washita, it must be in the upper 

 part of the strata, and not in the same bed with Gryphoia Pitcheri. 



The blue marl with Inoceramus problematicus was examined by Dr. 

 G. G. Shumard, in Grayson County, and it is given in the theoretical 

 section without saying what strata overlie or underlie it. From the 

 presence of the Inoc. problematicus in it, and of fish scales and teeth, 



