﻿118 PROF. E. W. SKEATS ON THE [Feb. IQO5, 



No. 32. From an immense fallen block, lower down the valley 

 than No. 33. (See PL X, fig. 2.) 



A large part of the slide consists of idiomorphic rhombohedral 

 dolomite-crystals. The crystals are cloudy, with inclusions 

 arranged parallel to their boundaries, and some of these inclusions 

 are calcite. The rhombohedra are porous on a minute scale, and 

 show the characteristic cleavages. The dolomite-crystals are set in 

 a background of large platy crystals of calcite, which show lamellar 

 twinning as well as cleavage. Signs of movement in the rock are 

 common, and no organisms remain. 



Area of the Sella. 



The following specimens were collected from the slopes of the 

 mountain, near the head of the Groden Pass. 



No. 101. Block fallen from above. 



The greater part of the section is composed of cloudy allotrio- 

 morphic dolomite-crystals, often arranged in a circular manner and 

 suggesting sections of corals. Empty spaces in the rock are lined 

 and nearly filled with clearer and more idiomorphic crystals of the 

 same mineral. 



No. 100. Near the summit of the Groden Pass. (PL X, fig. 1.) 



Large areas of calcite include partly- disintegrated organisms 

 resembling calcareous algae ( Splicer ocodium ?) which are only recog- 

 nized by a ' dirt-line ' marking the external boundary of the 

 organism. A few dolomite-crystals occur within the calcite-areas, 

 and are idiomorphic. Considerable areas of dolomite consist, how- 

 ever, of allotriomorphic crystals. 



No. 99. Fifty feet below No. 100. 



Very similar to No. 100. Large areas of calcite include imper- 

 fectly-preserved organisms, as well as a few rhombohedra of dolomite. 

 A fair quantity of allotriomorphic dolomite-crystals is present, and 

 includes irregular smaller patches of calcite, while exceedingly- 

 narrow strings and bands of calcite traverse the dolomite-areas of 

 the slide. 



No. 98. St. Cassian Limestone, immediately below No. 99. 



The rock consists mainly of calcite. The dolomite-crystals are 

 well seen only under the quarter-inch objective, and are for the most 

 part restricted to the matrix of one portion of the section in which 

 unaltered sections of calcite-shells occur. The majority of the 

 dolomite-rhombohedra have outer zones of chalybite, while a few 

 have a middle layer of chalybite, the inner and outer portions 

 consisting of dolomite alone. 



The St. Cassian District. 



Lavarella. — Collected from the cliff-face, in descending order. 

 No. 82. A cloudy, cavernous, fine-grained dolomite. The cavities 

 in the rock are partly or wholly filled with large idiomorphic 



