270 RESEARCH IN CHINA. 
discoid nodules of black chert. These nodules are flattened spheroids with 
a fairly uniform diameter of one or two centimeters. Black chert in thin 
strata, and less frequently in irregular nodules, is abundant at the top 
of this limestone member and at other horizons within it. A rock which 
suggests the middle Sinian limestone of northeast China is a gray half- 
crystalline oolite, which occurs abundantly in the talus upon these slopes. 
The cliffs expose massive strata of gray dolomitic limestone, some 
layers of which weather to a yellowish hue and others to an ashen white. 
Strata of similar appearance were noted in the interiors of anticlines at 
other points along the Yang-tzi and near the headwaters of the Ta-ning-ho. 
The thickness of the massive portion of the Ki-sin-ling limestone in 
the Nan-t’ou section is estimated at something more than 4,000 feet, 1,200 
meters, and for the lower slaty layers 200 to 300 feet, 60 to 90 meters, more 
should be added. Our search for fossils was without success, though we 
continued it during two hours on the lower cliffs and talus slopes near 
Nan-t’ou. 
On top of the characteristic Ki-sin-ling limestone, as it is exposed on 
the upper reaches of the Ta-ning-ho, there is an alternation of soft green 
caleareous shales with thin strata and nodules of limestones of gray and 
white colors about 200 feet, 60 meters, thick. These are separated from 
the overlying Sin-t’an formation by a hard light-colored limestone and 
thin stratum of dense black chert, lydite. In the shales and thin gray 
limestones there are abundant fossils. Dr. Stuart Weller has studied them 
and finds that they correspond closely with those of the Middle Ordo- 
vician or Trenton horizon of the eastern United States. In the more 
massive limestone directly beneath the shales there are also numerous 
well-preserved casts of Orthoceras. 
These fossils were first found at a rocky narrows on the Ta-ning-ho, 
about 1.5 miles, 2 kilometers, up the river from Sii-kia-pa (atlas sheet d 6). 
They occur in seams of thin gray limestone interbedded with green shales, 
which, in this locality, form a transition zone above the massive limestone 
and are 100 to 200 feet, 30 to 60 meters, thick. In these layers trilobites 
and brachiopods, with a few other forms, are exceedingly abundant. The 
collection from this station comprises the following recognizable forms: 
Cornulites sp. Vaginoceras sp. 
Lingula (2) sp. Ampyx sp. (cf. Ampyx costatus Boeck) 
Strophomena sp. Asaphus levis Weller 
Plectorthis willist Weller Asaphus sp. 
Dalmanella testudinaria Dalman Isotelus (2) sp. 
Clitambonttes chinensts Weller Megalaspis minor Weller 
Gastropod indet. Pretus sp. 
