CHAP. XII. 



Chiloe. 391 



amined are easily fusible, and some of the beds might 

 be called volcanic grit-stones. These latter strata are 

 perhaps related to a mass of columnar trachyte which 

 occurs behind Castro. The sandstone occasionally in- 

 cludes pebbles, and many fragments and layers of lignite ; 

 of the latter, some are apparently formed of wood and 

 others of leaves : one layer on the N W. side of Lemuy 

 is nearly two feet in thickness. There is also much 

 silicified wood, both common dicotyledonous and coni- 

 ferous : a section of one specimen in the direction of the 

 medullary rays has, as I am informed by Mr. K. Brown, 

 the discs in a double row placed alternately, and not 

 opposite as in the true Araucaria. I found marine 

 remains only in one spot, in some concretions of hard 

 calcareous sandstone : in several other districts I have 

 observed that organic remains were exclusively confined 

 to such concretions ; are we to account for this fact, by 

 the supposition that the shells lived only at these points, 

 or is it not more probable that their remains were pre- 

 served only where concretions were formed ? The shells 

 here are in a bad state, they consist of: — 



1. Tellinides (?) oblonga, G. B. Sowerby, PL II. f. 12 (a solenella 



in M. d'Orbigny's opinion). 



2. Natica striolata, G-. B. Sowerby, PI. III. f. 39. 



3. Natica (?) pumila, do. PL III. 1 38. 



4= Cytbersea (?) sulculosa, do. PL II. f . 14 (also Tpun and Huafo ?) 



At the northern extremity of the island, near S. 

 Carlos, there is a large volcanic formation, between 500 

 and 700 feet in thickness. The commonest lava is 

 blackish-grey or- brown, either vesicular, or amygda- 

 loidal with calcareous spar and bole : most even of the 

 darkest varieties fuse into a pale-coloured glass. The 

 next commonest variety is a rubbly, rarely well charac- 

 terised pitchstone (fusing into a white glass) which 

 passes in the most irregular manner into stony gray 



