Von Richthofen on the Nummuli tic formation in China. HI 



China, in particular to the mode of occurrence of the Devonian 

 limestone. 



I consequently visited the place a few days ago, on a journey 

 overland from Ningpo to Ching-kiang. As no limestone of 

 more recent age than the Devonian was heretofore known in 

 China, I was much surprised to meet with nummulites ahuost 

 at first sight, and afterward T found the rock in places nearly 

 made up of them. The rock is well exposed to view by enor- 

 mous quarries, which appeared to have been worked 'lor an 

 unmensely long time. The weathered surface of those frag- 

 ments covering the more ancient waste-dumps shows the struc- 

 ture of the shells with remarkable distinctness, even the minute 

 pores being clearly recognizable with a glass, so that there can 

 not be the least doubt in regard to the true character of the 

 fossil. Several species of Nummulina appear to be represented, 

 as is indicated by the differences in shape of the cross-sections. 



As Nummulites are characteristic only of one distinct part 

 of the Eocene period, the fact of their occurrence should be 

 sufficient evidence for the determination of the age of any 

 rocks in which they are met with. But I found myself now 

 in face of the strange fact, that it was partly on the strength of 

 its fossils that the limestone in question had heretofore been 

 considered as Devonian. I attempted therefore to collect its 

 fauna more fully. I found the roc^ in places full of fossils, 

 mostly bivalves and gasteropods, which have by no means a 

 Paleozoic appearance. They are in an excellent state of pres- 

 ervation, the shells being only bleached. But the limestone 

 is so hard and brittle that I destroyed nearly every specimen 

 which I tried to save ; yet I succeeded in getting a few good 

 ones of bivalves. The forms of these fossils, as well as their 

 state of preservation, reminded me much of similar occurrences 

 in the Nummulitic limestone of Dalmatia. Besides gastero- 

 pods and bivalves, there occur corals and fragments of very 

 large encrinites. Some of the former which I collected can 

 probably be determined. But I failed to discover a single 

 brachiopod, which are almost the only fossils supposed to be 

 characteristic of the Devonian limestone of China. I presume 

 that indistinct fragments of bivalves, which are usually all that 

 can be obtained, have siven rise to the belief of the occur- 

 rence of brachiopods on "the Si-Tung-ting. Perhaps, too, real 

 brachiopods may have been derived fi-om other places in or 

 near Tai-hu lake, as it is quite possible that true Devonian lime- 

 stone may occur in the neighborhood. 



The nummulitic limestone of Si-Tung-ting is very bitumm- 

 oiis. It is burnt in kilns and emits a remarkably strong smell. 

 Its thickness cannot be accurately determined, but it is certainly 

 not more than six hundred feet. ' Its beds are nearly horizuut: 1, 



