86 REPORT— 1873. 



sipliuncle, tliat sucli a power of adapting- the specific gravity of the shell must 

 have been very limited ; and he was disposed, on the whole, to believe that the 

 old Cephalopods, in rising and falling, trusted more to their strong arms than to 

 the filhno' and emptying of the pipe which connected the chambers. The subject 

 is under investigation. 



On the Ammonitie Septa in relation to Geological Time. By John Phillips, 

 M.A., F.B.S,, D.CL. Oxon., LL,D. Cambridge and Dublin, Professor of 

 Geologg, Oxford. 



The author, viewing the Ammonitidje as a family extending in time from the 

 Devonian to the Cretaceous period, proposed to examine into the genealogy of the 

 proper genus called Ammonites. He showed that from a supposed ancestral origin 

 in Goniatites, two lines of real or imaginary descent might be traced — one through 

 Ceratites of the Muschellvalk to the Cassianic ammonites, another through the 

 Arietes and other species of Lower Lias to the Upper Oolite and Cretaceous groups. 

 In neither case is the genealogy proved between the Carboniferous and later 

 families ; but in each case the change of septal outline (or " suture ") is from simple 

 Undulations to very complicated foliations. Such change, then, is only indicative of 

 successive time as it is characteristic of successive physiological change. Instead of 

 one development from Gonidtites, the most convenient form of hypothesis, at present, 

 would be to assume separate systems of development, each limited in time to 

 different periods, but following the same course of physiological change. The 

 same order of change occurs in the embryonic, yomig, and old shell of each species. 

 (The author hopes to make a further communication.) 



The Loess of Northern China, and its Relation to the Salt-basiiis of Central 

 Asia. B>j Bakon von Bighthopen, Ph.D. (Berlin). 



Northern China is covered with a yellow earth which resembles the Loess of 

 the valley of the Rhine in all essential properties. It is fine-grained and fusible, 

 yet so solid as to form vertical clifis and bluffs several hundred feet high, and dis- 

 tinguished by the complete absence of planes of stratification as well as a marked 

 tendency to vertical cleavage. It resembles loam in composition (its chief ingre- 

 dients being an argillaceous and ferruginous basis which contains very fine sand 

 and carbonate of lime in varying proportions), but differs from that earth by 

 possessing a highly porous and tubular structure. The tubes, which are very thin 

 and usually incrusted with a fine calcareous film, occupy in general a vertical posi- 

 tion, and ramify like the roots of grass. They cause the Loess to absorb water 

 like a sponge, and prevent the existence of any lakes on its surface, or the issuing 

 of springs from the body of the formation, although these are copious where the 

 earth rests on rocks or stratified soil. The Loess encloses bones of land-animals 

 and an abimdance of well-preserved shells of terrestrial mollusca, but no marine 

 or freshwater fossils. Calcareous concretions are always disseminated through it, 

 and mostly arranged in well-defined layers, in which, as a rule, the longer axis of 

 each nodule occupies a vertical position. 



The Loess is peculiar to Northern China, no trace of it occurring in the southern 



firovinces; it is observable on the side of Mongolia and Central Asia, just to the 

 imit of the headwaters of those rivers which flow towards the sea, covering 

 altogether an area of about 240,000 square miles. Within this area it spreads 

 alike over low and high ground, from the level of the sea to altitudes of 8000 feet, 

 its thickness varying from very little to upwards of 1500 feet. It smooths off" the 

 irregularities of the surface, and, by connecting with each other the crests of 

 distant mountain-ranges, created between them large trough -like basins with gently 

 inclined slopes, the bottom of each'of which is made up of stratified earth which 

 otherwise resembles Loess in appearance and is strongly impregnated with 

 .alkaline salts. The sides of each basin are furrowed by innumerable and infinitely 

 ramified gullies, which frequently attain the depth of 1500 feet. With the exception 

 of the great alluvial plain adjoining the lower Hwangho, human habitations and 



