MARCOU: THE JURA OF TEXAS. 
157 
At the Tuoumcari area, above a well-defined Trias we have a 
series of white and yellowish sandstone, resting conformably and 
without interruption on the variegated and red marls of the Keuper. 
At the Tucumari area, no fossil has yet been found in this white 
and yellow sandstone, but in eastern Texas and western Arkansas 
fossils occur and belong to the Jurassic fauna and flora. Capping 
this sandstone we have at the Tucumcari a series of blue clay with 
vellow limestone, resting conformably on it as a continuation of the 
series of almost horizontal strata. In this series we have at two 
places, Pyramid Mount and Kent Station, an important fauna, the 
two most characteristic fossils of which are the Gryphaea Tucum- 
carii and the Ammonites ( Schloenbachia ) Shumardi. The great 
majority of the fossils belong to Jurassic forms, only two or three 
having any generic affinities with Cretaceous forms of Europe. 
They are clearly representative in America of the Upper Jura, 
called in the southern part of Europe the Tithonian series of Albert 
Oppel. 
Then a great break occurred and deposits of strata, discordant in 
stratification, on the Trias at Comet Creek, Indian Territory, Fort 
Washita, Texas, and other places, began a new series containing a 
Lower Cretaceous or Neocomian fauna. The first strata of this 
Cretaceous system contain at Comet Creek, Fort Washita, etc., an 
immense number of Gryphaea Romeri Marcou (formerly called G. 
Pitcher % by Romer and Marcou). The Gryphaeae are so numerous 
as to recall the “Limestone of the Gryphaea arcuata ” of the Lias 
of England, France, and Germany. These first beds, which may 
be called “ Caprina and Gryphaea Romeri limestone,” are the bot¬ 
tom beds of the American Neocomian or Lower Cretaceous. With 
such characteristic and abundant fossils as Gryphaea Tucumcarii 
Marcou, Ammonites (/Schloenbachia) Shumardi Marcou, and Gry¬ 
phaea Romeri Marcou, no confusion or mistake is possible. The 
first two indicate the Upper Jurassic or Tithonian formation of 
Texas and of New Mexico, and the third, the beginning and first 
beds of the Lower Cretaceous, called by Marcou Texas Neocomian 
and by Hill Washita formation or division. 
A very careful and exact study of what are called the Bosque 
and Fredericksburg divisions is now of first importance, and is 
much needed. It may be regarded as already conceded that sev¬ 
eral of the beds of the Fredericksburg division are local and proba¬ 
bly equivalent to some if not all of the Bosque beds. 
