18 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
that the Aylmer formation of the Ottawa Valley region is to be correlated with 
the Valcour formation, uppermost Chazy. This correlation is chiefly based on 
the common presence of Rostricellula plena in the Ottawa formation and the 
Valcour of New York. Few other fossils are common to the two sequences 
because the facies are quite unlike. 
Ottawa group (or formation) 
This name is taken from the Ottawa Valley and embraces a number of units 
that were hitherto regarded as formations. Dr. Wilson believes that the fos- 
sils indicating certain time units do not conform with lithologic boundaries of 
the formations that had been previously defined. In order to make Ottawa stra- 
tigraphy more practical and more easily understood Dr. Wilson recommends 
abandonment of the formations that had hitherto been recognized: Pamelia, 
Lowville, Leray, Rockland, Hull, Sherman Fall, and Cobourg. This problem 
occurs in many sequences that have been refined by paleontological work, such 
as the Southern Appalachians. Here a number of geologists have attempted to 
divide the Chickamauga limestone on the basis of fossils, but shifting facies make 
boundaries cloudy and the geologist uninitiated in fossils finds the separation of 
formations difficult. This has inspired a recent effort to revive the name Chicka- 
mauga as a formation. Inasmuch as one purpose of the present work is to portray 
in detail brachiopod assemblages, I prefer to recognize the named faunas in both 
the Ottawa and Chickamauga limestones, realizing at the same time that the 
boundaries between divisions are in many cases uncertain. 
Pamelia formation.—In the Ottawa Valley this formation is composed of 
two divisions, the lower one characterized by its large proportion of sandstones 
and sandy shales. Thin layers of dark limestone, some fine-grained and others 
dolomitic, also occur. The upper Pamelia consists mainly of gray limestone and 
beds of dolomitic material, separated by shale partings. A few sandy layers ap- 
pear, but the upper beds are distinguished from the lower ones by a lesser sand 
content. The division between the upper and lower Pamelia and between the 
Aylmer underneath and the Lowville above the Pamelia are transitional and 
difficult to determine. The two divisions of the Pamelia are estimated to attain 
at least 69 feet in thickness. Fossils are rare in the Pamelia but one of the im- 
portant ones is the trilobite Bathyurus extans Hall. Brachiopods reported by 
A. E. Wilson (1946a, pp. 3-9) are: 
Camerella panderi Billings = Idiospira panderi (Billings) 
Lingulella narrawayi Wilson 
Strophomena canadensis Wilson 
*S. filitexta Hall 
S. minuta Wilson 
S. venustula Wilson 
Correlation of Pamelia formation—The Pamelia of the Ottawa Valley has 
many characteristics of the New York or type Pamelia and is probably related 
to it. Although the Pamelia was placed in the Chazyan by Ulrich (1911, pl. 27) 
its affinities seem rather to be with the overlying Lowville than with the Chazy. 
