282 T. S. Hunt—History of the Pre-Cambrian Rocks 
VAcad. Royale de Ja Belgique for 1876; and Memoire sur la Comp. Minéralo- 
gique du Coticule, by Renard, from the same for 1877. Also Gosselet and Malaise, 
Terrain Silurian des Ardennes, Bull. Acad. Roy. de la Belgique (2) No. 7, 1868; 
Dewalque, Terrain Cambrien des Ardennes, Ann. Soc. Géol. de la Belgique, tom. 
i, p. 63; and farther, Hunt, Chem. and Geol. Essays, p. 270.] 
APPENDIX. 
Since the above paper was read the author has received (No- 
vember, 1879) a private communication from Prof. L. W. 
brook, consisting chiefly of petrosilex rocks, and an upper 
division, the typical Huronian, called by him the Coastal group. 
Britain, where it has a prevailing strike of N.N.E. and 
S.S.W., or from this to N.E. and SW.” In addition to the 
localities which we have already mentioned in Great Britain, 
e notes its occurrence in Shropshire and in Charnwood 
Forest, and also in the northwest of Scotland, where, as else- 
an 
and with the Petrosilex series which the writer has made 
known in America. In addition to the localities already men- 
tioned of it in the British Isles, Hicks notes its occurrence 17 
