1891.] Geology and Paleontology. 49 
of M. ii. at anterior cross-crest, 48 mm.; do. at posterior cross-crest, 38 
mm. ; do. of M. iii. at anterior cross-crest, 45 mm. ; anteroposterior 
diameter of do. at inner base of crown, 42 mm.—E. D. Cope. 
The Tertiary Formations of Western Texas.—Mr. Robert 
T. Hill has made brief mention in three short papers! of a very inter- 
esting fact concerning the age of the Staked Plains, and the extent ot 
the fresh-water Tertiary formations of the West eastward into the Texas 
region. The whole of the great mesa known as the Llano Estocado 
and some of the basins of the Trans-Pecos region, near El Paso, are 
composed of the sandy loams, grits, and pebbles of this formation. 
This area in Western Texas and Eastern New Mexico extends in places 
eastward to the one hundredth meridian, and is a direct continuation 
southward of the same formation in Kansas and Nebraska, Its south- 
ern limit on the Rio Grande is near Del Rio, and the whole area, which 
is as large as New England, has hitherto been colored Cretaceous and 
Jurassic upon previous maps. The formation has afforded fossil bones 
in various places; but these as yet have been unstudied. It rests un- 
conformably upon the Comanche series, the Jura Trias, and the various 
rocks in the mountain ridges. Everywhere at its base it affords an 
abundant supply of well water, which has proved of great value to the 
settlers who are now rapidly locating on the Staked Plains. The Fort 
Worth and Denver road traverses the formation from Clarendon to 
Tascosa, and the Texas Pacific from Sweetwater to the Colorado valley, 
and from thence westward. ‘This additional knowledge upon the 
former extent of the great inland lakes of Tertiary times is important 
in that it nearly doubles the areal extent hitherto acknowledged, and 
enables us to locate the narrow continental divide between the Gulf 
of Mexico and the Tertiary lakes with greater accuracy. Dr. Otto 
Lerch has corroborated the extent of these beds in a recent article on 
the Concho country, in the American Geologist for 1890. The great 
development of this terrane in Southern New Mexico, was pointed out 
by Prof. Cope, in the Proceedings of the Amer. Philos. Society, 1883, 
p. 308. 
The Eighth Volume of Reports of the Geological Survey 
of Illinois left the press in July last. The general distribution of the 
edition—s5,000 copies—must, however, be postponed until the Legis- 
lature of the State will have provided for its binding. Only fifty 
-= Copies have been bound in advance, and we have received one of them. 
We will give a full notice in future number of the NATURALIST. 
‘Notes on the Geology of Western Texas. Bulletin Texas State Geological Soc., 
, 1888. Pro. Am. Ass, Adv. of Science, Toronto, i. 168) Torger and 
Geology of T Texas Region. Am. Geologist, Jan., 1890. 
Am. Nat.—January.—4. 
Mo. Bot. Garden, 
1895. 
