﻿36 



GEOLOGICAL MEMOIRS. 



On this hippurite limestone reposes another limestone formation, 

 consisting of a number of parallel beds of no great thickness, the 

 principal fossils in which are various Foraminifera, of which the 

 most remarkable belong to the genus Nwnmulites. This nummulite 

 limestone, which, like the hippurite limestone, is covered with a 

 scanty vegetation, affords ample matter for speculation. In the 

 neighbourhood of Trieste it forms only a narrow band in the Karst 

 mountains, and its beds dip conformably to the main dip of the 

 range, at an angle of about 40° to the sea. To this there is one ex- 

 ception. Near the village of Contovello a road was commenced some 

 years ago, and afterwards abandoned; but a new one has since been 

 completed leading from Trieste to the plateau of the Karst : the view 

 of the surrounding landscape from this spot is very beautiful, which 

 is partly due to the beds of nummulitic limestone, which here are not 

 only vertical, but for some distance along the sea-shore form a mural 

 precipice above 100 feet high, overhanging the macigno. With this 

 single exception, the nummulite beds range with the dip mentioned, 

 forming a narrow zone between the hippurite limestone and the 

 macigno from S. Croce to the defile of Bolliunz, near the summit of 

 the escarpment of the Karst. It is to be observed, that near the 

 junction with the hippurite rock, the Foraminifera in the nummulite 

 limestone are almost of microscopic minuteness ; and it is in the 

 "pper beds that the forms become larger, the number of species in- 

 creased, and the number of individuals incredibly great. The elegant 

 forms of Alveolina long a, A. subpyrenaica, of Melonites, and of 

 other species probably not hitherto described, are found in great 

 abundance. As the beds approach the macigno, it is clearly obser- 

 vable that species of larger dimensions and of natter proportions are 

 introduced. Circular valleys, similar to those in the hippurite lime- 

 stone, occur also in the nummulitic, as well as cavities between the 

 beds ; but neither so well developed as in the hippurite rock. 



I have described in a former memoir * the limits of the nummulite 

 limestone and the macigno ; it is therefore only necessary for me to 

 refer my readers to that paper, and to add that the results contained in 

 it are perfectly in accordance with those obtained at a later period 

 from more extended observations. 



The macigno, which forms all the country immediately around 

 Trieste, can best be studied in its vicinity, and is highly interesting 

 from the much-contested question, whether it be the equivalent of 

 the Vienna and Carpathian sandstones, which it so closely resembles 

 in a mineralogical point of view. Though covered in many places by 

 a luxurious vegetation, yet the new roads which have been cut to 

 Opchina and to Fiume, the numerous stone quarries, and an abrupt 

 sea-coast, afford many opportunities for observing this formation. 



Wherever it is observed in the vicinity of Trieste, near its junc- 

 tion with the limestone, its lowest member is a thinly cleaving, grey- 

 ish-blue marl. The locality at Contovello mentioned above, where 

 the beds of limestone for a short space are vertical, is an exception, 

 and not an unimportant one. The circumstance of the prevalence of 

 * Haidinger's Berichte, vol. iv. p. 158. 



