LIMESTONES OF SOUTH DEVON. 379 



from indications on weathered surfaces, gave hopes of interesting 

 slides being obtained from it. When, however, these were made 

 the rock was found to be made up almost entirely of the remains of 

 crinoids, some of which are remarkably well preserved. 



(c) Lummaton Limestones (Upper horizon of the Middle Devo- 

 nian). — At Lummaton, near St. Mary Church, there is an extensive 

 quarry in white crystalline limestone. From this rock thin sectious 

 gave the following results when examined with a microscope : — 



No. 1. Entirely crystalline ; no sign of organisms can be detected. 

 Several rhombohedral crystals of dolomite occur. 



No. 2. Microscopic examination of this slide shows that the lime- 

 stone has also undergone considerable molecular change. Calca- 

 reous fragments of undoubted organic origin occur, but the struc- 

 ture is mostly obliterated and there is often little else but a granular 

 mass left. Among these organic calcareous fragments are portions 

 of coral and ossicles of crinoids. 



No. 3. Similar to the last. Rhombohedral crystals of dolomite are 

 numerous, mostly as single crystals, which are slightly tinged with 

 iron. 



Specimens were also collected from Barton Quarry, situated 

 about half a mile from Lummaton. The limestone in which this 

 quarry is opened is for the most part less crystalline than that 

 quarried at Lummaton, but it is otherwise similar. The following 

 slides were made from it and examined : — 



No. 1. Very crystalline; no sign of organic structure could be 

 detected. The limestone is altered, but a distinction can be drawn 

 between the original organic portion and the infilling calcite. 



No. 2. This is mainly a coral limestone with a quantity of infilling 

 calcite. 



No, 3. This limestone also shows signs of molecular change. 

 There is a quantity of infilling calcite and of dark granular frag- 

 ments, some of which can be recognized as the remains of corals, 

 mollusca, &c. ; in others the outlines of organic structure cannot be 

 detected. There are also numerous crystals of dolomite present, 

 mostly in aggregates (PL IX. fig. 1). 



(d) Coomb End Limestone. — Coomb End, near Kingsteignton, is 

 situated between Teignmouth and Torquay. The quarry from 

 which the specimens were taken is opened in a limestone in which 

 no bedding could be traced. 



Three specimens, collected respectively from the base, middle, and 

 top of the quarry, show coralline structure. 



Apparently the Coomb End Limestone represents an old coral- 

 reef, and this explains the absence of bedding. 



(e) Loiuer Dunscomhe IJmestone. — The specimens were obtained 

 from a quarry at Whiteway Earm, near Chudleigh. The limestone 

 is indistinctly bedded, and in colour is dark. 



Specimen No. 1 shows a more or less dark granular groundmass 

 traversed, in part, by fissures. One or two obscure fragments of 

 organisms can be traced, and among them the ossicles of crinoids. 



No. 2. Full of organic calcareous fragments, but these are much 



