10 . GEOLOGICAL MEMOIES. 



Silica 36 per cent. min. 71 per cent. max. 



Alumina 6 „ „ 38 „ „ 



Iron oxides „ ,, 36 ,, „ 



Magnesia ,, „ 29 ,, „ 



Potash 2 „ „ 14 



Lithia „ ,, 5-7 ,, „ 



Fluor „ „ 104 „ 



Water is present up to about 4 per cent., and organic matter is 

 occasionally found in considerable quantity, as for instance in the 

 lithia-mica of Altenberg, which is treated in quantities of 16 cwts. 

 at a time for the production of lithia. 



Serpentine forms the subject of chapter xxxix. ; it is considered 

 throughout as a product of alteration, the view of its igneous origin 

 being distinctly repudiated. In like manner in the chapter on 

 quartz and other forms of silica the views of the so-called " Plu- 

 tonists " are combated to the uttermost. The volume is closed by 

 two chapters on magnetic and titanic iron-ores considered as pro- 

 ducts of the alteration of silicates, a view which is not generally 

 held in countries where those minerals are most abundant, as in 

 Scandinavia and Forth America. [H. B.] 



On the Brachiopods cmcl other Bivalves of the St. Cassian Beds. 

 By Dr. Laube. 

 [Proceed. Imp. Acad. Sciences, Vienna, March 23, 1865.] 

 The Brachiopods of St. Cassian offer a greater analogy in their 

 general facies with those of the Palaeozoic period than those of the 

 Mesozoic deposits, as Prof. Suess has already observed with respect 

 to the Brachiopod-fauna of the Hallstatt strata. At all events, the 

 St. Cassian strata represent an important period in the development of 

 this class, three Palaeozoic genera, Cyrtina, Dav., Sjpirigera, D'Orb., 

 and JRetzia, King, finding in them their last representatives ; while 

 Spiriferina, D'Orb., not ascending above the Lias, first appears in 

 the St. Cassian strata. Among the other Brachiopods, Waldheimia 

 and Thecidium are Mesozoic; and KonincJcina, ^uess, and Am^hi- 

 ceina, Laube, are peculiar to the strata in question, and are transi- 

 tion forms between the Palaeozoic and the Mesozoic typical genera. 

 Among thirty species described, ten are new. Only a small number of 

 the fifty species described by Count Miinster and lOipstein have 

 proved admissible, many of them being merely young forms of 

 established species. The Bivalve-fauna bears a more general cha- 

 racter, including however representatives of the typical Triassic 

 genera, Cassianella, Beyr., Myophoria, Bronn, and Ilornesia, Laube. 

 This last genus, named after Dr. Homes, comprises the GervilUce of 

 the " Muschelkalk," bearing the type of G. socicdis, Schloth, and 

 differing from the genuine GerviUice by the peculiar structure of 

 their hiuge, and by a more or less lengthened septum going through 

 the cavity of their umbones. Only about half the number of species 

 estabhshed by Count Miinster and Klipstein proved to be admissible 

 after close examination, many of them having been established on 

 mere fragments, not offering any decisive characters, or on figures 

 of questionable accuracy . Of seventy Bivalves described by Dr. Laube, 

 only eight are new. [Count M.] 



