PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 23 
The formation thins to the east and west of its area of greatest thickness. It 
thins to disappearance in Oneida County, N. Y., to the east, and Okulitch reports 
the Shadow Lake formation, equivalent of the Pamelia, as only 18 feet thick in 
the vicinity of Coboconk, Ontario. 
The upper member is more persistent than the lower one. The formation is 
also marked by shallow-water phenomena such as ripple marks and mud cracks. 
Fossils are rare in this formation. Cryptophragmus is present in the lower divi- 
sion. Ancistrorhyncha sp.=A. costata Ulrich and Cooper and Zygospira recur- 
virostris (Hall) are the only brachiopods reported by Young (1943, p. 234) in 
his extensive studies of this formation. 
The age and affinities of the Pamelia formation have been the subject of con- 
siderable debate (Young, 1943, p. 151) but it is generally conceded now that 
it has its strongest ties with the Lowville rather than with the Chazy group. 
This is certainly the indication given by the few fossils that have been taken 
from it. The two mentioned brachiopods place the Pamelia fairly high. Zygo- 
spira in the Appalachians is not known until the time of Witten deposition, but 
Ancistrorhyncha is slightly older. The Pamelia appears to be a part of the Low- 
ville and probably varies in age from place to place. 
Lowville formation.—This name has been widely used in the eastern United 
States and Canada as a formation name, but such use should be discouraged 
outside of New York, Ontario, and Quebec. Only in these latter regions can 
the formation be shown to be a laterally continuous unit. Elsewhere the name 
has use only in a facies sense for so-called dove limestones. 
In its type region the formation is 34 feet thick but a short distance away it is 
54 feet thick. It thins to the southeast to 6 to 10 feet in the Mohawk Valley. 
To the west it is 40 feet thick at Kingston and 47 feet at Marmora, Hastings 
County. Okulitch records the Gull River formation, equivalent of the Lowville 
at Coboconk, as 45 feet. The formation is divisible throughout its extent into 
a lower and upper part, the former generally thin bedded and the latter heavy 
bedded. In Ontario the Lowville usually is shalier than in New York. 
The lithologic types seen in the Lowville are dove-gray and dark sublitho- 
graphic limestones usually in thick beds and often with calcite-filled worm bor- 
ings and tangled nets of the coral Tetradium cellulosum. Dark semicrystalline 
and argillaceous limestones are often interbedded with the sublithographic beds. 
Granular beds and oolites also occur. The lower beds are often conglomeratic 
and the formation rests disconformably on the Pamelia or on Canadian rocks 
where the Pamelia has been overlapped. Mud-cracked and ripple-marked shales 
indicate shallow-water deposition. 
Fossils are fairly common in Lowville rocks but the preservation is often poor 
and it is difficult to extract specimens from the sublithographic limestones. The 
following brachiopods are reported: 
*Rafinesquina minnesotensis = Opikina 
*Rhynchotrema sp. cf. increbescens (Hall) 
Strophomena sp. 
Zygospira recurvirostris (Hall) 
