90 KEPORT— 1869. 



Since Prof. Sedgwick and Sir R. Miu-cliison proposed to substitute " Devonian " 

 for " Old Red Sandstone " very much lias been done, by very acciu'ate observers, 

 with respect to the latter local accumulations. It has been ascertained to be cer- 

 tainly a duplex, if not a triplex group, each division being dependent on contem- 

 poraneous physical changes, and each of which may be representative of the three 

 severally distinct stages, on the systematic marine scale ; namely, of part of the 

 Upper Silurian of Sir R. Murchison's system, of the true " Devonian," and, lastly, 

 in some cases of the Lower Carboniferous period. 



The great geological interest which attaches to the ti-ue " Old Red Sandstone " 

 consists in this — that, as does the " Hm-onian " for an earlier Pala3ozoic stage, and 

 as does the Piu'beck-Wealden group for the great break in the Secondary (Jurassic 

 and Cretaceous) formations, it serves hj its magnitude to illustrate the vast lapse 

 of time which really separates the marine groups of formations which geologists 

 place in immediate sequence, and serves also to show the nature of the subaerial 

 operations of the time. 



Owing to the length of the communication the second part, relating to the geo- 

 graphical distribution of the Devonian marine faxma, was not read. 



Notes on the Dlscoveri/ of some Fossil Plants in the Cambrian (^Upper Long- 

 mynd) Rocks, near St. David's, By Dr. Hicks. 



The plant-impressions occur on some thin layers of shale facing the surfaces of 

 rough grit-ljeds, at a place called Treller\vi-, two miles to the east of St. David's. 

 These beds form a part of the section whicli underlies the " Menevian " rocks of 

 the well-kuo\sni creek of Porth-y-Rhaw, and belong to the same series of grey 

 beds as those in which the fossils, mentioned in the author's paper read at the 

 Norwich Meeting last year, were discovered ; they are lower down than the 

 zone of the Trilobites (a hivalved crustacean and Lim/idcUa ferriKjinea ha^e 

 been discovered over 800 feet deeper in the section). These beds are strongly 

 ripple-marked, and give indications of having been deposited in shallow water. 

 The ones immediately above, and which contain the other fossils {Plutonia Sedg- 

 wiclci, Conoconjphe LyeUii, &c.), are of a finer grain, and indicate a somewhat deeper 

 water-deposit. No other fossils have ]}een discovered as yet along with the 

 plant-impressions, though, as already stated, others occur below, and also almost 

 immediately above. These beds are entirely separated from the "Menevian 

 gToup " by a good thickness of purple and red rocks. 



One of the specimens exhibited was obtained by the author some years ago from 

 the " Menevian group;" it was shown because of some amount of resemblance to 

 the plants just found. This, however, came from a deep-sea deposit, and is there- 

 fore most probably a distinct species. 



The Extinction of the Mammoth. By H. H. Howoeth. 



After a survey of all the authorities within his reach, the author concluded that 

 no existing theory accoimted for the following facts, which are indisputable : — 



1. That the Mammoth lived in the area where his remains are foimd. 



2. That a great portion of that area is now a moss-covered tundra, or an ice and 

 boulder heap, as in the Bear Islands. 



3. That no herbivore of the size and plentiful development of the Mammoth 

 could find food in that area now. 



4. That although covered with wool, and therefore adapted to a much more 

 rigorous climate than that of India and Africa, neither Mammoth nor Rhinoceros 

 could survive the present winter temperature of Northern Siberia. 



5. The remains of the food eaten by the Mammoth and Rhinoceros, found and 

 exam in ed by Midderndorft' and Brandt, are remains of plants only found now in 

 more southern latitudes. 



The only possible conclusion from these facts is, that the climate and condition 

 of things in Siberia have altered very greatly since the days of the Mammoth. In 

 support of this conclusion, such facts as the following are conclusive : — the bed of 



