[HOWARD] SOME OUTLIERS OF THE MONTEREGIAN HILLS 



55 



tical mound rises to the south of a small stream running parallel with 

 the railroad. It is composed of alnoitic rocks which outcrop within 

 an area approximately 600 yards long by 250 yards wide; the long 

 axis lies north-east and south-west parallel to the road running south- 

 west from the river road near Como, and the exposure is bounded on 

 the north by the small stream. 



The mineralogical composition of the various types on monti- 

 cellite alnoite at Como is as follows: 



aa Very Abundant 



a Abundant 



b Subordinate 



c Present 



As at Isle Cadieux, there are textural variations in the rock, the 

 principal type containing porphyritic biotite occupies the greater part 

 of the intrusion, while on the north and south sides of the exposure 

 the fine grained minette-like type, similar to that noted by Bowen at 

 Isle Cadieux, can be found in which the mica is less than one millimetre 

 in diameter. The relations between this type and the principal type 

 could not be determined owing to the paucity of outcrops. 



Principal or Porphyritic Type. — The principal rock type of the 

 exposure is a dark grey fine-grained rock which is plentifully speckled 

 by poikilitic biotite crystals up to 5 mm. in diameter. This rock 

 is slightly finer than the principal type described by Bowen at 



