378 ME. E. WETHERED ON THE DEVONIAN 



crinoids. Ehombohedral crystals of dolomite similar to those 

 uoticed in the Calceola Beds are here also present. 



Higher up in the quarry weathered surfaces of the limestone 

 show that it is largely made up of coral debris, polyzoa, and stro- 

 matoporoids, the latter, in some instances, growing round portions 

 of coral. Thin sections of the rock confirm this, interpretation and 

 show that the structure of the coral-fragmeuts is well preserved. 



Towards the middle of the quarry the coral limestone disappears 

 and is followed by a series of beds very dark in colour. Thin sec- 

 tions show an almost structureless groundmass traversed in all direc- 

 tions by infilling calcite, the whole suggestive of an original tubular 

 structure. Some aggregations of tubules can be made out, and in 

 these the tubules measure 0*2 mm. in diameter (Plate IX. fig. 3). 

 They resemble the tubules of Girvanella, but there is no clearly 

 defined wall ; they are, apparently, forms of vegetation. There are 

 also present ossicles of crinoids, valves of ostracoda, and one or two 

 fragments of shell. All these have the appearance of being enclosed 

 by the groundmass. As to the nature of the original organic struc- 

 tures now represented by this groundmass there is no clear evidence 

 on which to base an opinion ; but it is suggestive of a vegetable 

 growth that has enclosed the calcareous organisms whose remains 

 appear in it. 



A portion of this limestone was dissolved in hydrochloric acid, 

 and with the ultimate residue was 4* 6 per cent, of black material of 

 very slight specific gravity, which disappeared on ignition in a plati- 

 num crucible. There is little doubt that this substance was carbon, 

 a fact which gives support to the view that the groundmass in this 

 limestone is, in part at least, of vegetable origin. 



(b) Daddy Hole Limestones. — The specimens were collected in a 

 quarry opened out at the sea-level. Commencing near the bottom 

 of the quarry, on the Torquay side, dark limestone occurs. Thin 

 sections show a groundmass and tubular aggregations similar to 

 those noticed in the dark limestone at Hope's Nose, but in some 

 instances the outlines are nearly obliterated. Several fragments of 

 organisms are present, including ossicles of crinoids and one or two 

 fragments of coral. As in the case of one of the slides from Hope's 

 IS'ose, the groundmass appears to have enclosed the fragments of 

 organisms which are noticed in it. 



The next specimens were collected from a limestone at a higher 

 horizon, containing yellow patches which might at first sight be 

 taken for concretions. jVlicroscopic examination, however, has not 

 confirmed this supposition, but shows a structure very like the 

 groundmass referred to in previous slides. 



Other sections of this limestone show an absence of the ground- 

 mass noticed in slides of the yellow patches, and prove that it is 

 made up of very fragmentary calcareous organisms ; among these 

 fragments, corals and echinodermata, the latter probably ossicles of 

 crinoids, the main outlines of which have been obliterated, may be 

 traced. 



Near the top of the quarry is a bed of limestone which, judging 



