1882. 1 
315 
[Davis. 
The occurences in the feldspar and augite are unmistakable 
while those in the groundmass are more doubtful, owing to its 
confused nature. Some seven crystals of picotite were counted 
in one feldspar. It is very abundant in the olivine, even more 
so than he had observed it in the olivine of other basalts from 
the Pacific coast. In two cases groups of unmistakable picotite 
crystals were seen partly in the feldsjiar and partly in the oli- 
vine, forming a united chain. This discovery of picotite, out- 
side of the olivine, the speaker had looked forward to, in 
accordance with his views of the relation of the olivine of 
basalts to the magma (Bull. Mus. Comp. Zool. 1879, V, 277-281). 
General Meeting. January 18, 1882. 
The President, Mr. S. H. Scudder, in the chair. Thirty-four 
persons present. 
The following paper was read : 
ON THE CLASSIFICATION OF LAKE BASINS. 
BY WILLIAM 
Introductory. 
Earlier Classifications. 
A. Construction or Orographic 
Basins. 
1. Great Basins. 
2. Mountain Trough Basins. 
3. Fault “ 
4. Warped Valley “ 
5. Earthquake “ 
6. Volcanic Subsidence “ 
7. Solution Subsidence “ 
B. Destruction or Erosion Basins. 
1. Glacial Erosion Basins. 
2. Wind Erosion “ 
3. Solution “ 
4. Pit-Crater “ 
MORRIS DAVIS. 
♦ 
C. Obstruction, Barrier or Enclosure 
Basins. 
1. Fan Delta Barrier Basins. 
2. Ice Barrier “ 
3. Moraine Barrier “ 
4. Drift Barrier “ 
5. Lava Barrier “ 
6. Sand Bar “ 
7. Barrier Reef “ 
8. River Lagoons. 
9. Land Slip Barrier Basins. 
10. Beaver Dams. 
11. Delta Enclosure Basins. 
12. New Land Basins. 
13. Glacial Drift “ 
14. Crater Basins. 
15. Coral Island Lagoons. 
O 
