24. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Chaumont formation.—This name was proposed by Kay (1929a, p. 644) 
for rocks occupying the interval between the Lowville and the Rockland in 
Jefferson County, N. Y. The name was made to include three members in 
ascending order: Leray, Glenburnie, and Watertown. The Leray member con- 
sists of 13 feet of heavy-bedded, dark brownish-gray to black limestone con- 
taining considerable chert. This member in the type region of the Chaumont 
is separated from the Watertown by 2 feet of fossiliferous shale, the Glenburnie. 
The Watertown limestone, or top member, comprises 13 feet of massive lime- 
stone without chert except for the lower part. Outside the type area it is diffi- 
cult to separate the Leray and Watertown. 
The Chaumont formation thins to the south and east and is absent at Middle- 
ville, N. Y., and in the Mohawk Valley. When the formation is followed to the 
west it tends to become thinner bedded, browner, and with chert absent, irregu- 
larly spread through it, or confined to the top. The formation is also less easy 
to separate from the Lowville but the faunal content is persistent. The forma- 
tion attains as much as 25 feet in thickness north of Peterborough, Ontario, but 
thins again in the vicinity of Lake Simcoe. 
Brachiopods are fairly common and varied in the Chaumont formation: 
*Camerella volborthi Billings 
Doleroides gibbosus (Billings) 
D. pervetus (Conrad) 
*Glyptorthis bellarugosa (Conrad) 
*G. insculpta (Hall) 
Hesperorthis tricenaria (Conrad) = H. concava Cooper 
Hesperorthis sp. 
Leptaena radialis Okulitch = Cyphomena ? radialis (Okulitch) 
Pionodema sp. 1 
Rafinesquina clara Okulitch = Opikina clara (Okulitch) 
R. minnesotensis (N. H. Winchell) = Opikina minnesotensis (N. H. Winchell) 
*Rhynchotrema sp. cf. increbescens (Hall) 
*Strophomena sp. cf. delicatula Fenton 
Strophomena sp. 
“Valcourea deflecta (Conrad)” 
Zygospira recurvirostris (Hall) 
Rockland formation.—This term refers to beds overlying Chaumont and 
underlying Hull limestone. The formation is typically developed in Ottawa Val- 
ley but occurs also in western New York and Ontario. The formation is 64 feet 
thick east of Dexter, N. Y., and is of similar thickness in Lennox and Addington 
County, Ontario. Two members have been distinguished in New York and 
Ontario: Selby member and Napanee member. 
Selby member of Rockland formation—Kay (1937, p. 252) proposed this 
name for dark-gray to black, medium- to fine-textured, petroliferous thin-bedded, 
buff-weathering limestones characterized by the brachiopod Doleroides ottawanus 
Wilson. The member is recognized in New York in Jefferson County where it 
extends southeast to about East Martinsburg in the Black River Valley, in 
Lewis County. At Lowville, N. Y., it is about 15 feet thick. It is exposed in 
