[174 ] 300 
Ne. Y67 fs ak” impure limestone, but little harder than common chalk; 
and, but for its associations, would be regarded as of similar origin. 
- 106 is apparently a vitrified sandstone, the grains all rounded, and 
No. 94 is a mammillary or botryoidal lava ; the concretions having a ra- 
diated structure, the mass is easily frangible, and readily separates into small 
The whole of this series, with the exception of No. 107, may be regard- 
ed as of voleanic origin ; for the apparently vitrified sandstone may. be, in. 
its composition, not very distinct from trap or basalt, though it is more vit- 
Re SP 
mens appear as if from some regular formation, broken up and thinly coat- 
ed by calcareous matter from springs. From the fact observed by Captain 
water origin. ere are also some vertebre and ribs of fishes. The 
whole is so unchanged, and of such recent appearance, as to induce a belief 
that the deposite is of fresh-water origin, and due to the desiccation of some 
to’an agricultural community will be an important consideration. But, as 
before remarked, there is evidently a preponderance of calcareous matter 
rsed 
of much older date, and worn very round and smooth, while the limestone 
bears little evidence of attrition. 
he gray siliceous limestone. specimens contain aspecies of Turritella, 
and a small bivalve shell. (See descriptions and figures.) _ ; 
Longitude 1154°, latitude 433°.—The two i nip aed ar loeality are 
of voleanic origin. No. 46 is a reddish compact trap or lava, with small 
nodules or cavities filled with analcime and stilbite. No. 52 is a coarse 
and Porous trap, or ancient lava. + 
Longitude 116°, latitude 433°.—The Single specimen from this place is 
ae 2 
ho finds it highly charged with <‘ calcareous polythalamia” in excellent pr / 
tion. He remarks, that ‘*the forms are, many of them, such as are common in chalk and cretaceous 
marls; but as these forms are still living i t i ce not afford con- 
clusive evidence as to the age of | deposite in which they occur. I have, however, invariably 
era peculiar to the tertiary, — ow, as these are entirely wanting in the specimen from Captain 
_ Frémont, the evidence, as far as it ‘coves, is in favor of the view that the specimen came from a 
n oF 
