The Dlas, Triox (n^'^ Jura in Texas. — Marcos. 373 
rlty cannot be used for geographical names of the Tucumcari 
area. 
In the Mfi.nns isisf'cs (variegated marls) of Plaza Jjarga no fossils 
have been found, either by Mr. C'ummins or myself; but farther 
south-eastward, in continuity of the strata, Mr. Cummins has col- 
lected fragments of Stfijocephali. CrocodUui. Clejysysdnnis and 
Zatomas. Above the variegated marls, so easy to follow bed by 
bed at the Pyramid mount section, we find a series of about 200 
feet of white and yellow sandstone, l)lue clay, calcareous sand- 
stone and at the toj) a white limestone. The fossils begin to be 
found in the blue clay, al)0ut 80 feet thick. A bed, two inches 
thick, of Grijplia<i. dildtatd var. tucHmairii, packed close together, 
is found at half a foot from the base; and more of those Gryphna 
tucamrtirii can be collected higher up, in the whole group of Idue 
clay, with an Ostrt'd of the Ostna DiarsJiii form. Those two 
fossils are characteristic Jurassic species, and indicate that the 
age of the blue clay is Oxfordian. 
Mr. Cummins accepts the Gnjp/iwn dilahitit var. fiii-inii<tiri.i as 
a good species distinct of the Gryplma pitclurl of the Texas Neo- 
comian; but it is his only concession. In a special chapter, en- 
titled: "Notes on the geology of the country west of the Plains 
— ^Tucumcari, New Mexico,'" pp. 2(11-210, in the Thinl Am). Rep. 
GeoJ. Sure. Te.itis. Mr. Cummins contests the exactness of my 
conclusion in regard to the Jurassic age, and he refers the Tu- 
cumcari beds to the Cretaceous, and in that system to the Wash- 
ita division; that is to say. to the upper part of the Lower Cre- 
taceous, above the Trinity division, and even al>ove the Com- 
manche Peak and Fredericksburg division. 
LithidiHjij. — Mr. Cummins has a long and useless dissertation 
on lithology, saying that I committed an error, to call '-Calcare- 
ous sandstone or sandy limestone" the strata above the l)lue clay 
with Grijphmd. fucnmnu-ii, which he calls, also, like me. -Calca- 
reous sandstone." It is exactly the same definition, and even the 
same name. In my wood-cut section of Pyramid Mount (see 
The American Geologist, Oct. 1880, p. 1()2), for brevity of the 
table of explanation of the letters used to designate each bed, I 
used onl}' -'Yellow limestone, "" but in the description of the strata 
I call them "Yellowish siliceous limestone," and in "N'ol. Til, Pn- 
ctfir RdUrodd E.rjdordflons, '- Calcareous sandstone. ' 8o there 
is no ground whatever for a discussion. I have cmIUmI llic l)ed9 
