Structure of the Austrian Alps, &>c. 133 



has been carefully re-examined ; and we are enabled, through 

 the kind assistance of our friend Mr. J. de C. Sowerby, to give 

 the following results. 



Out of more than one hundred different species (collected 

 by ourselves on the spot) there are from thirty to forty bi- 

 valves ; and of those capable of being identified, nearly equal 

 numbers are referrible to the youngest secondary, and the 

 oldest tertiary formations*. The univalves are much more 

 numerous, especially in the quantity of each species; a fact 

 seldom remarked in secondary deposits. Among upwards of 

 fifty species, three only are found in the chalk or green-sand, 

 whilst seven species are identical with known tertiary fossils ; 

 and several of the genera, such as Volvaria, Pleurotoma, and 

 Voluta, have, we believe, seldom if ever been found in any de- 

 posit below the surface of the chalkf. 



After all these facts and observations, we venture to reaffirm 

 those conclusions which in previous memoirs we have endea- 

 voured to establish. 



1. That in association with different parts of the eastern 

 Alps, is a fine succession of tertiary deposits, commencing with 

 some of the oldest and ending with some of the newest which 

 have hitherto been described. 



2. That the older tertiary deposits of the Austrian Alps 

 sometimes ascend far within the transverse valleys, and in such 

 cases rest unconformably upon the beds of secondary lime- 

 stone. 



3. That the same deposits are developed, in many places, 

 on the outskirts of the chain ; and do in such cases pass un- 

 der, and graduate into, those newer deposits to which alone 

 M. Boue would restrict the name of tertiary. 



We now return to the southern extremity of our transverse 

 section (PL II. fig. 1.) Although there is a general accordance 

 in the successive zones of secondary rock on each side of the 

 central axis, it will be seen, even on the minute scale of our sec- 

 tion, that the tertiary deposits of the Friuli form only inconsi- 



* The secondary species are: Myaplicata; Corbula elegans ; Trigonia 

 scabra; T. alaeformis; Pecten quinquecostatus ; Exogyra laevigata; E.conica; 

 Terebratula dimidiata : Cucullaea carinata. The tertiary species are San- 

 guinolaria Hollowaysii; Cytherea laevigata ; Cardium hippopaeum ; Pec- 

 tunculus nummarius; P. auritus; P. pulvinatus; P. brevirostris ; Nucula 

 similis. 



f The three univalves, identical with species in the chalk or green-sand, 

 are : Auricula incrassata ; Cirrus granulatus ; Rostellaria calcarata. The 

 seven tertiary species are : Pleurotoma prisca ; Fusus bulbiformis ; F. in- 

 tortus; Rostellaria macroptera; Mitra pyramidella; Voluta citharella; 

 V. coronata(P). 



IV. S. Vol. 8. No. 44. Aug. 1830. Q derable 



