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GEOGNOSTIC OCCURRENCE. 



Hitherto this fossil has been only found in the high Hiesen 

 mountains, which separate Silesia from Bohemia, near the 

 origin of the Iser, dispersed through the granitic sand which 

 forms the bed of that river. To what order of rocks it owes 

 its origin is uncertain; but its near affinity to iron sand, 

 which is exclusively an inmate of the flbtz trap formation, 

 and the certainty, that this formation was formerly super- 

 stratified, at a great elevation, on the Riesen mountains, (as 

 the remains, which form the Bnchberg,* and occupy the 

 Schneegruben, sufficiently testify,) render it highly probable, 

 that this fossil, also, may belong to that formation; and, 

 consequently, dates its origin from a much more recent 

 period, than the foregoing Species of this genus.-f 



* The Buchberg (which I enjoyed the invaluable opportunity of examining 

 ■with my excellent and ever to be regretted friend) is the highest basalt hill in 

 Germany, being 2921 feet above the level of the sea, and the highest basalt, 

 except that small quantity lodged in the cavity of the Schneegruben, which is 

 some hundred feet higher. The hill itself is elevated about 500 feet above the 

 Iser, that washes its granitic basis, and the Iserine is found at some distance 

 below. We could, indeed, discover no trace of it in the basalt of the present 

 hill.— R. J. 



t Mr. Giregor (as stated in Nicolson's Journal) has found, that menac is 

 one of the constituent ingredients of basalt ; a fact, which adds much to the 

 plausibility of Dr. Mitchell's very ingenious supposition. — R. J, 



E 3 GENERAL 



