﻿Vol. 6l.] DOLOMITES OF SOUTHERN TVROL. 139 



EXPLANATION OF PLATES X-XIV. 



[The rock-sections are preserved in the Author's private collection, but 

 numbered hand-specimens of the rocks from the Dolomites have been deposited 

 at the British Museum (Natural History). The Author is indebted to his 

 friend, Mr. Franklin T. Barrett, for the photographs from which these Plates 

 have been prepared.] 



Plate X. 



Fig. 1. Slightly-doloinitized limestone (No. 100), from the Sella, X 11 diam. 

 Sporadic rhombohedra of dolomite are scattered through the rock, 

 which contains badly-preserved calcareous algae, foraminifera, and 

 other organisms. (Stained with Lemberg's solution.) 

 2. Dolomitized limestone (No. 32) from the Marmolata. X 32 diam. 

 Some of the dolomite-crystals are allotriomorphic ; but those pro- 

 jecting into calcite are well-formed, and show cloudy zones. (Stained 

 with Lemberg's solution.) 



Plate XI. 



Fig. 1. Dolomite (No. 10), from the Schlern. x 32 diam. Dolomitization is 

 so nearly complete that no calcite remains, and the large majority of 

 the dolomite-crystals are allotriomorphic. A few crystals with cloudy 

 centres exhibit, however, rhombohedral outlines. 

 2. Oolitic and partly-dolomitized St. Cassian Limestone (No. 77) from 

 St. Cassian. x 50 diam. The oolitic grains are well-preserved, show 

 both concentric and radiating structure, and include foraminifera and 

 fragments of other organisms. Minute rhombohedra of dolomite 

 occur in the calcite-matrix, but do not extend into the oolitic grains. 



Plate XII. 



Fig. 1. Buchenstein Limestone (No. 88), from the Gader Gorge. X 230 diam. 

 A limestone containing zoned crystals, consisting of calcite and dolo- 

 mite in alternate layers, which are in crystallographic continuity. 

 The calcite-layers are stained with Lemberg's solution, and appear 

 dark in the illustration. 

 2. Transverse section of a coral (No. 109), from the St. Cassian Limestone 

 of Sett Sass. X 18 diam. The original aragonite and the minute 

 structure of the coral remain. The stages in the conversion of 

 calcareous mud into clear crystalline calcite are also shown. To 

 this change the preservation of the coral is probably to be attributed. 



Plate XIII. 



Fig. 1. Part of No. 109, more highly magnified, x 240 diam. The middle 

 line of the septa is shown, as also prismatic crystals of secondary 

 aragonite, formed in crystallographic continuity with the coral-fibres, 

 which project from the walls of the coral into the space between the septa. 

 2. Dolomite 0), from the stream at Bad Ratzes. X 30 diam. The dark 

 areas probably represent septa of a coral, the structure of which has 

 been largely destroyed by dolomitization. The lighter dolomite-crystals 

 in the matrix show cloudy zones. 



Plate XIV. 



Fig. 1. No. 112. Schlern Dolomite of Sett Sass. X 11 diam. Transverse 

 section of organisms (Gyroporellal), the structure of which has been 

 destroyed by dolomitization. The dark crystals defining the outer 

 margin of the organisms have originated by the extrusion of im- 

 purities during the process of recrystallization. 

 2. Insoluble residue from partly-dolomitized coral (No. 37), from the Giau 

 Pass. X 250 diam. The insoluble residue consists entirely of very 

 minute, doubly-terminated crystals of quartz, showing occasional 

 distortion and striation on the prism-faces. 



