20 
GEOLOGY 
nally between Inscription Rock and the Pueblo of Zuni, wdiere it again forms mesas, which extend 
in the direction of Fort Defiance and the Canon de Chelly. It will be seen that these rocks of the 
Llano Estacado occupy, geographically, a large place in the Geology of the Rocky Mountains ; but 
as regards their relative age, they are still more important, for they fill a void until now left in 
the series of stratified rocks of North America; these rocks belong to the Jurassic or Oolitic epoch. 
Fossils are very rare in the sandstone and limestone; hut the beds of blue clay which are found 
in the middle of this formation contain in abundance a Gryphwa which has the greatest analogy with 
the Gryphcea dilatala of the Oxford clay of England and France, and which I call provisionally Gry- 
pheea dilatala var. Tucumcarii (Plate IV., fig. 1., 1 a, 1 b, 2. and 3.)') ; and a very large ustrea having much 
resemblance to the Ostrea Marshii (Plate IV. , fig. 4.) of the Inferior Oolite of Europe. I found also 
a Trigonia and a species of Astarte resembling very much the Astarte Duboisiana d’Orb. of the Juras- 
sic formation of Moscou (See: Geologie de la Hussie et de I'Oural, par Murchison, de Verneuil et de 
Keyserling; vol. II., page 455.). This American Jura.ssic presents, at least thus far, one point of 
considerable difference from the Jurassic of Europe and Asia, where such large quantities of Cepha- 
lopods are found, such as Ammonites and lielemnites-, while here the Ammonites are only found in the 
Green-Sand, and the Belemnites in the Marly Chalk; and even there, these fossils are never so abun- 
dant as in the corresponding strata of Europe. 
In a practical point of view the Jurassic Rocks are rather poor. The limestone will furnish 
lime ; the sandstone can he used for embankments and bridges , and with some advantage over that 
of the Trias, for it is harder. Finally, in some localities, as at El Ojo Pescado near Zuni, in the 
neighbourhood of Fort Defiance, at the Canon of Chaca, there are beds of bituminous coal in the 
clay, but only three or four inches thick, so that probably they would not be rich enough to be 
successfully worked. 
Continuing our itinerary, we find that from Anton Chico to near San Antonio we are almost 
constantly on white and yellow Jurassic Sandstones. Three miles before reaching San Antonio, 
the Trias is met with again , which now is found upheaved and dislocated , the strata dipping to the 
East (See: the Profil gMogigue du Fort Smith au Pueblo de los Angeles; on the same plate with the Geo- 
logical Map'); and for a space of five miles, all the Triassic strata are passed through, with the gyp- 
sum, dolomite, sandstone and red clay — exactly the same sort of rocks that were seen before 
in the Trias of the Prairies. Immediately on leaving the village of Tigeras, which is situated in 
the middle of the Pass that crosses the Rocky Mountains , called here Sierra de Sandia , also Al- 
buquerque Mountains; black schistose clay is seen, belonging to the Coal-measures, then grayish 
blue limestone, containing a great quantity of fossils. These last strata of schist and limestone are 
very much upheaved, dipping to the East at an angle of 30 or 40 degrees; they rest on metamor- 
phic rocks. The principal fossils found in the limestone, which belongs to the Mountain Limestone or 
Lower Carboniferous^), are: Productus semi-reticulatus , P. cora, P. Flemingii. P. punctatus , P. pustulosus 
1) See Chapter III., Paleontology; ■where I describe several new species of fossils found in the centre 
of the continent. 
2) Having reached Albuquerque, New Mexico, the 5"' October 1853, the expedition remained there 
until the 10“’ November, to recruit the strength of the party and prepare for crossing the Californian desert. 1 
profited by this interval to explore the country comprised between Albuquerque, San Antonio, Pecos and 
mtm 
