384 RESEARCH IN CHINA. 
CONGLOMERATIC LIMESTONES. 
In the case of these rocks I depart from the general plan of the report 
and discuss them collectively. 
In general.—limestones composed of pebbles set in a calcareous 
matrix are characteristic of the Cambrian formations in the four northern 
provinces of China, viz: Liau-tung, Shan-tung, Chi-li and Shan-si. In 
Shan-tung they occur most abundantly in the Ch’ang-hia and Ch’au-mi-tién 
formations, and especially near the contacts of these members with the Ku- 
shan shales; but they were also observed locally at other horizons from the 
lower part of the Man-t’o shales to the top of the Ch’au-mi-tién limestone. 
The rocks have already been described, in a brief way, by von Richthofen.* 
By him they are given the expressive name of “ Wurmkalk,’’ a term which 
has the advantage of not committing the author to any theory regarding 
the origin of the pebbles. Very recently they have been redescribed by Dr. 
Theo. Lorenz,} from observations made in Shan-tung. Rocks of a similar 
nature are reported from the Cambrian terranes of North America—notably 
Montana, Wyoming, Texas, Indian Territory, and the Appalachian moun- 
tains. The occurrences in the United States have been described and inter- 
preted by Walcott{, under the name of “‘intraformational conglomerates.” 
The conglomerate layers are associated with calcareous shales and 
shaly limestones. The beds themselves are rarely more than 3 or 4 feet 
thick, but there is frequently a succession of the conglomeratic layers sepa- 
rated by thin beds of shale or dense limestone, and all together forming a 
comparatively thick series. In a few of the conglomeratic beds, in the 
upper part of the Man-t’o shale, cross-bedding is sometimes observed. One 
important fact to be noted regarding the conglomeratic limestones is that 
single layers often preserve a nearly constant thickness over areas several 
miles in extent. WalcottS has emphasized the fact that the conglomerates 
usually occur entirely within formations and thus do not mark uncon- 
formities. 
The pebbles.—In the several specimens which we collected in China we 
find among the pebbles a wide range in size and shape. The smallest are 
less than 1 millimeter in length; the majority measure from 2 to 5 centimeters 
and the largest slightly exceed 10 centimeters. Rounded flattish forms 
prevail, the pebbles closely resembling the variety of gravel which consists 
of water-worn fragments of slaty rocks. Bodies of globular shape are not 
common and sharp corners are quite rare. Under the microscope it is 
observed that the edges of the pebbles are usually smooth and evenly 

* Von Richthofen: China, vol. 1, pp. 74, 79-80, 190. 
} Lorenz: Beitrage zur Geol. u. Paleont. von Ostasien, Marburg, 1905, Teil 1, p. 12. 
t Walcott, Bull. G. S. A., 1894, v, pp. 191-198. 
§ Loc. cit. 
