276 ROYAL SOCIETY OF CANADA 



The White Horse Eapids occurrence is included tentatively, the 

 information available not showing the relation of the monchiquite. 

 Monchiquite, however, is closely related to alnoite. 



From this table it is seen that the breccia may be divided into two 

 distinct classes, according to whether the matrix is an alnoite or a 

 nepheline aplite rock. The alnoite class includes quite definitely the 

 occurrences at La Trappe, He Bizard and Ste. Anne, while those at Ste. 

 Helen's Island and St. Paul Street very probably belong here also. The 

 Medical Building occurrence is unimportant. The Cote St. Paul ma- 

 terial coming from a boulder, no definite locality can be assigned to it; 

 however, on account of the interesting fossils it contains, an important 

 point has been gained in limiting its derivation to this series, and so 

 proving that these fossils have come from this vicinity. The one occur- 

 rence of camptonite may be classed with the alnoite group with which 

 it is related. 



The nepheline aplite class is represented solely by the masses at 

 Westmount. 



Since it has been shown that so many of these breccias have an 

 alonite paste, it is proper to note here the other three alonite occurrences 

 of the district, previously studid. Two of these have been described, by 

 Dr. P. D. Adams. The first is a typical alonite dyke found near Ste. 

 Anne de Bellevue ^ which cuts the Potsdam sandstone and contains frag- 

 ments of that and also the underlying Laurentian formations. The 

 second is near St. Lin 2 twenty-four miles north of ]\Iontreal. Although 

 the rock is very much decomposed, the sections show" that it is very closly 

 comparable with the occurrence at La Trappe described in this paper. 

 The third locality is Point St. Charles, two miles south of Ste. Helen's 

 Island and was examined by Mr. Allan in the course of his study of the 

 dyke rocks of Montreal. This is a dyke corresponding almost exactly 

 wiîh the alnoite of Isle Bizard. 



SUMMAKY OF RESULTS. 



It will be noted that the occurrences of breccia are found lying 

 along the western extension of the line of the Monteregian Hills. 



The breccia has as a wall rock strata of widely different ages, ranging 

 from the Laurentian gneiss to the Trenton and Utica. The occurrence 

 in the Utica on Ste. Helen's Island, however, while cutting the Utica and 

 containing fragments of all the formations down to the Laurentian 

 gneiss, is remarkable in that it also holds inclusions of formations strati- 



iF. D. Adams, Am. Jour. Sc, 3rd Series, Vol. XLIII, pp. 269-279, 1892. 

 2 F. D. Adams, Geol. Survey, Canada, Ann. Rept., Vol. VIII, pt. J., p. 136. 



