159 
DIVISION STREET AND Dow LAKE. 
Upper Trenton and Collingwood.—Near the corner of 
Somerset and Division streets isa quarry in the Hormotoma 
trentonensis beds at the top of the Trenton. This quarry has 
furnished many rare echinoderms, and is the type locality for 
Steganoblastus ottawaensis, for certain crinoids described by 
W. R. Billings, and for two species of sponges described by 
Hinde. The fauna of these beds reminds one strongly of the 
Black River, Ischadites iowaensis, Trochonema umbilicatum, 
Illenus americanus and various species of Subulites and 
Fusispira being found here. Not all these fossils can be 
found here, but Hormotoma trentonensis, Rafinesquina 
delioidea, Illenus americanus, and Cyclospira bisulcata are 
not uncommon. 
In a quarry situated on Division street south of the 
crossing of the Grand Trunk railway the upper part of the 
cystid beds is exposed and Agelacrinites and Pleurocystites 
are found in them. The western border of this 
quarry is just on the line of the fault between the Trenton 
and the Collingwood, and this fault crosses Division street 
just below Norman street. 
The low area below Rochester and Preston streets 
at the north end of Dow lake is underlain by the Colling- 
wood formation, and as extensive sewer trenches have been 
dug here in the last few years, a considerable amount of 
fossiliferous material is available along the streets in this 
district. This is the type locality for Oxyplecia calhount, 
and entire specimens of the characteristic Collingwood 
asaphoid, Ogygites canadensis, have been found here. The 
upper Trenton beds come in beneath the Collingwood west 
of Preston street and Dow lake, and when the water is 
drawn off, the western side of Dow lake is an especially 
good collecting ground for Cyclospira bisulcata. 
The upper part of the cystid zone and the lower part 
of the Hormotoma trentonensis zone are exposed in quarries 
on Carling avenue, LeBreton and Bell streets. 
HOGSBACK. 
Aylmer and Pamelia Formations.—Hogsback is a 
point on the Rideau river south of Ottawa where the 
Rideau. canal leaves the river. The strata in 
the bed of the river at Hogsback form a low 
