Notices of Memoirs — Daubree on Native Platinum. 561 



A list of the graptolites of the Ludlow rocks given in a former 

 communication to the British Association (1873) was then referred 

 to, 1 and the main conclusions as to the distribution in these rocks near 

 Ludlow of the species enumerated, arrived at in the course of a few 

 days spent in this neighbourhood before the opening of the present 

 meeting, were given. 



It was shown that several species of Mbnograptus abound in the 

 lowest beds of the Lower Ludlow ; that some of these pass up and 

 a few others come in a little higher in the series, all in soft cal- 

 careous sandy shales ; and that when a decided change in the strata 

 takes place, indicating in some places, by more siliceous and gritty 

 beds, comparatively shallow water deposits, and in others, by ex- 

 cessively hard fine-grained limestones, a deeper sea, a decided change 

 in the graptolite fauna occurs, the gritty beds containing in myriads 

 a single new form, Mbnograptus Leintwardensis, and the indurated 

 limestone alone yielding the few - species of Ptilograptus which have 

 yet been detected. Mbnograptus colonics, Barrande, a form first seen 

 in the Llandovery rocks, appeared to be the only species which sur- 

 vived these physical changes, it having alone been seen in the softer 

 beds high in the Lower Ludlow, and passing up from these into the 

 harder calcareous shales which in some places immediately underlie 

 the Aymestry Limestone, and again passing uprinto- this limestone 

 bed, in which it seems finally to disappear. 



The author concluded by showing the dependence of the fossil 

 fauna and flora of these rocks on the physical conditions of the 

 Lower Ludlow seas, the fossils frequently being only locally dis- 

 tributed', and varying slightly in their horizons according to the 

 nature of the sediment deposited, the graptolites especially being 

 influenced by these changes, to which their final extinction, or at 

 least their dispersion from the area under consideration, was con- 

 sidered to have been most probably due. 



To the list previously given, a single species- only, Monograpius 

 Boemeri, Barrande, occurring in the lowest beds of the Lower Lud- 

 low, is added by these recent researches. 



II. — On the Association of the Native Platinum of the Urals. 



DAUBREE, in an interesting paper read before the Academy of 

 .» Sciences, has shown that Native Platinum, although obtained 

 abundantly in the alluvial deposits of certain regions of the Ural, has 

 been found in a Peridote (Olivine) rock, which is more or less altered 

 into serpentine, and accompanied with diallage (a ferruginous sahlite, 

 according to M. Des Cloizeaux), and also with chromite, which 

 occurs abundantly, not only in separate grains, but also encrusting 

 the grains of platinum. The platinum, which is here associated with 

 chromate of iron, appears to be distinguished from the platinum of 

 other deposits by the large proportion of metallic iron with which it 

 is alloyed. It appears that platinum very rich in iron, and endowed 

 with magnetic polarity, has not been found — at least, at present — ■ 

 save in company with chromate of iron. — " Comptes Bendus," t. lxxx. 

 —March, 1874.— J. M. 



1 See Geol. Mag. Yol. X. p. 520. 



