128 DKEDGINGS OF THE MAKINE BIOLOGICAL ASSOCIATION: 



microcline twinning. By far the greater part is probably, however, 

 oligoclase. Quartz abundant, in large areas of compound structure. 

 The quartz is traversed by narrow streams of fluid inclusions, and 

 contains small rod-shaped crystals, apparently of apatite. Both 

 massive and actinolitic hornblende occur. The pleochroism of the 

 former is pale yellow-brown, dark olive-green. At places a vivid 

 chlorite replaces some of the hornblende. The quartz is slightly iron- 

 stained in some of the cracks. Quartz hornblende diorite. 



Four rocks apparently similar to the group M. 9e., M. 9r., and M. 19a., 



are — 



(1) M. lib. S. 26° W. Edd., 17'8 miles. 



Dark grey granitoid rock of fine grain. 



(2) M. Ilk. 



A finer texture of M. lib. 



(3) M. 9q. 



Dark grey, fine grained, felspars greenish. 



(4) M. 50a. S, 16^ W. Edd., 30-9 miles. 



Grey crystalline rock, minutely granular fracture, rather 

 small white felspars somewhat widely scattered. 



M. 18a. S. 29° W. Edd., 23-4 miles. 



Structure granitic, medium texture, colour grey. 



Somewhat clouded felspar, apparently plagioclase. Graphic structure 

 in many crystals. Quartz traversed by broad streams of fluid inclusions, 

 some with bubbles ; hair-like microlites also occur, and some larger, 

 recognizable, apatite. There are two micas, the one colourless, the 

 other brown and intensely pleochroic, the extreme tint being a very 

 dark bronze green. Quartz mica diorite. 



M. 58a. S. 22° W. Edd., 39 miles. 



Black and grey granitoid rock, medium grain. 



Granitic texture. Felspars in the main clear, but here and there 

 clouded with decomposition products. All apparently plagioclase and 

 probably oligoclase. The quartz clear, with small fluid inclusions and, 

 at places, hair-like microliths. Brown and oli^'^e-brown mica, strongly 

 pleochroic. Green and olive hornblende, always associated with mica, 

 but on the whole in less quantity. The hornblende and mica inter- 

 penetrate. A fair amount of apatite is present. 



The rock must be classed as a quaitz-diorite, with hornblende as 

 well as mica present. 



M. 80d. S. 16i° W. Edd., 489 miles. 



Fine-grained brown granitoid rock, with black mica, texture granitic. 

 Felspar much altered and crowded with brown decomposition pro- 



