PART T CHAZYAN AND RELATED BRACHIOPODS—COOPER 17 
R. williamsi Okulitch = O. wagneri (Okulitch) 
*Rhynchotrema increbescens (Hall) 
Strophomena corrugata Okulitch = Strophomena okulitchi Cooper 
*S. emaciata Winchell and Schuchert 
*Strophomena incurvata (Shepard) 
No formations correlative with Rockland are known in the vicinity of Montreal. 
OTTAWA VALLEY, VICINITY OF OTTAWA 
Ottawa and vicinity have long been known for the interesting fossils described 
from the Ordovician rocks that underlie the city and surrounding country. Here 
an interval from the Lower Ordovician (late Canadian) through the Richmond 
is exposed. 
Aylmer formation.—This name was used by Raymond (1905, p. 362) for 
the Chazy rocks in this region. Recently the formation has been divided into 
two formations, one of shale and sandstone, the other of limestone, which are 
at least partial facies of each other and would be better considered as members 
of the Aylmer formation. The Aylmer formation extends from L’Orignal west 
to Alumette Island, about 115 miles. In its westernmost localities the limestone 
is not present. 
Rockcliffe member of Aylmer formation.—This name is applied by A. E. Wil- 
son (1946a, p. 17) to the lower part of the Aylmer formation, which consists of 
predominantly green shale containing lenses of fine, gray sandstone. It is named 
for Rockcliffe Park, just east of Ottawa. In places the basal layer is a con- 
glomerate. This member has an average thickness of about 160 feet. 
Brachiopods reported are: 
Camarotoechia orientalis Billings = Rostricellula orientalis (Billings) 
C. plena (Hall) = R. plena (Hall) 
Hebertella imperator (Billings) = Mimella imperator (Billings) 
Lingula lyelli Billings = Ectenoglossa ? lyelli (Billings) 
Lingulella rugosilinea Cooper 
Lingulella sp. 6 
Mimella latistriata Wilson 
Rostricellula wilsonae Cooper 
St. Martin member of Aylmer formation—This member is named by A. E. 
Wilson (1946a, p. 19) from Cap St. Martin, north of Montreal, where I give it 
formation rank. The member consists of about 20 feet of gray or brown shales, 
gray-green sandstones and impure limestones, and dolomites which weather to 
a rusty brown. East of Ottawa, deep wells indicate that the member thickens to 
150 feet. Dr. Wilson reports four zones in the St. Martin, the lowest containing 
several species of Hebertella (=Mimella) with a few specimens of Camaro- 
toechia (=Rostricellula) orientalis. In the second zone the proportion of the 
two genera is more nearly equal; in the third zone R. orientalis becomes much 
more abundant. The fourth zone abounds in Camarotoechia (= Rostricellula) 
plena with R. orientalis. 
Correlation of Aylmer formation—Raymond (1905, p. 362-364) has shown 
