268 
Aug. F. Foerste 
Proetus ranges from the 533 to the 1002-foot levels, in de- 
scending order. At the 820-foot level, the Pterotheca pentagona, 
here described, was found. Leptaena occurs also at the 1284, 
1338, 1515, 1699, and 1878-foot levels. Above the highest Lep- 
taena horizon, at the 820-foot level, all of the forms of Catazyga 
resembled Catazyga headi. Between the 820 and the 1284-foot 
levels no specimens of Catazyga were noticed. At the 1284-foot 
level some poor specimens of Catazyga were found which could be 
identified only generically. Catazyga erratica was identified with 
certainty only at the 1390-foot level. The first specimens of 
Trinucleus, in descending order, are found at the 1552-foot level, 
and it has been followed below this level, at various intervals for 
fully 800 feet without reaching the base of its range in these strata. 
Triarthrus is known at present only from the 1653-foot level. 
The association of Triarthrus, Trinucleus, and Leptaena, seen on 
the Yamaska River, northwest of St. Hugues, is correlated pro- 
visionally with this 1653-foot horizon in the Nicolet River section. 
This, probably, is the horizon also of the exposures on the Becan- 
ceur River, about a mile and a half east of Breault station. The 
exposures southwest of Petite Caroline, containing Leptaena, and 
reported to contain Trinucleus, apparently belong somewhere 
between the 1550 and 1880 foot levels. The exposures at St. 
Hyacinthe are regarded as lower than anything studied so far 
along the Nicolet River, and those at St. Augustin and at the 
Montmorency Falls are regarded as far lower. 
A considerable part of the fauna collected along the Riviere 
des Hurons, west of St. Jean Baptiste, has not been recognized 
as yet elsewhere. Owing to the presence of Whiteavesia of the 
pholadiformis group, and the absence of Proetus, however, these 
strata are correlated with the upper part of the Nicolet River 
section, somewhere between the 77 and 220-foot levels. It 
should be remembered, however, that Whiteavesia of the pholadi- 
formis type occurs also at Chambly, and that the presence of a 
fossil is a safer guide to its stratigraphical position, than the ab- 
sence of an expected form. 
