68 
Pror. D. S. Martin showed specimens of muscovite 
lately brought to view in blasting gneiss rock at Rye, 
Westchester Co. The crystals were remarkable for their 
elegant cleavages, especially for a set parallel to 7 3. 
He also exhibited a series of magnesian minerals lately 
procured from the old serpentine locality at New Rochelle, 
comprising marmolite, deweylite, magnesite, and chromite in 
‘serpentine; and remarked upon them in connection with the 
facts referred to at the last meeting, as illustrating still fur- 
ther the points then presented. He had visited the locality 
for the purpose of examining its mineralogy; and his expec- 
tations in regard to its character were abundantly verified. 
The general features that mark the eastern, or Huronian, ser- 
pentines, in distinction from those of the Blue Ridge and 
Kozoic districts, were plainly to be seen. 
Mr. W. P. JENNY gave an account of his recent explora- 
' tions in the geology of Western Texas. His principal line of 
travel had been across the Llano Hstacado, near the 32d 
parallel, to the Pecos River, and on to the Rio Grande near 
EH] Paso. 
The first important formation encountered was, of course, 
the Cretaceous of the Llano Hstacado, (Jurassic of Marcon). 
A section from the base, near the Pecos, gives: 
(A.) Red sandstone, 50 feet, like the Trias of the Eastern 
States, underlaid by, and probably resting on, a gneiss. 
(B.) Soft, brown sandstone (Cretaceous?) passing upward 
into limestone, 50 feet. 
(C.) Great limestone, 450 feet, rich in typical Cretaceous 
fossils, Hxogyra Texana, Gryphea FPitcheri, Ammonites 
pedernalis, etc. 
(D.) On the mesas, here and there, are found some 40 feet 
of a limestone full of Caprina, but usually worn away by 
denudation. 
The sharp edges cf the Llano are very remarkable, gener- 
ally much sea-worn. No drift action was visible; though 
occasionally on these edges there occur local beds of small 
jasper and chalcedony pebbles. 
The next important point noted, was the great develope- 
ment of Carboniferous limestone in the Guadaloupe moun- 
tains, the most eastern of three main ranges that lie between 
the Llano and the Rio Grande. The rocks here dip eastward, 
