Professor Epwarp Hutn—On the Nature and Origin of Beds of Chert. 81 
forms a deeply channelled section of a spine of an echinoderm (Archzocidaris ?) is 
apparent. (Analysis IV.) 
No. 6. Dark chert ; same locality as No. 5 but different bed.—Traces of organic 
structures obscure. Numerous small crystals of calcite inclosed in the silica and 
perfectly formed. 
No. 7. Dark chert, compact, same locality as No. 5.—Organic forms numerous, 
but obscure and difficult of determination, probably chiefly foraminiferal. Contains 
25°4 per cent. of carbonate of lime. (Analysis V.) 
No. 8. Dark brown compact chert, same locality as No. 5.—The whole field 
shows organic forms more or less distinctly, consisting of crinoidal stems, polyzoa, 
foraminifera, and fragments of bivalves(?) ; external forms only preserved, interiors 
of clear structureless silica. The intermediate spaces of gelatinous silica sometimes 
contain minute granules grouped in twos and threes and joined at the margins. 
Their origin is uncertain. 
No. 9. Dark compact calcareous chert interposed between bands of limestone 
containing fossils, Florence Court Park.—The whole field shows organic forms, 
amongst which sections of foraminifera and ossicles of crinoids may be distinguished. 
In general the forms are fragmental and arranged in parallel layers. The portion 
of the specimen analyzed by Mr. Hardman is a siliceous limestone. (Analysis VI.) 
No. 10. White fossiliferous chert with laminated structure, from Upper Lime- 
stone of Bonnet’s Rath, near Kilkenny.—Beds just below the Yoredale shales. 
Specimen consists of colourless amorphous paste inclosing numerous organic forms 
chiefly foraminiferal(?) which come into view with the aid of the polariscope 
There are also a few minute crystals of calcite inclosed. This specimen contains 
but very little lime. (Analysis VIL.) 
No. 11. Black compact chert with traces of fossils, from Bonnet’s Rath quarry.— 
This specimen shows a wavy laminated structure, and with the aid of the polariscope 
faint organic structure throughout. Black grains of carbon(?) and crystals of 
calcite and silica are also inclosed. Proportion of lime slightly greater than in last. 
(Analysis VIII.) 
No. 12. Compact black chert in irregular bands from Ballyfoyle, near Kilkenny. 
—Parts of beds fifty feet thick, just below the Yoredale shales ; shows colourless 
paste mottled brown, with a few black grains, some cubical in form (probably 
pyrites) ; organic structure not apparent in this case. Well formed crystals of 
pyrites slightly decomposed, and of a slightly translucent copper colour along the 
edges; also diffused masses and grains of waxy yellow matter without structure, 
probably native sulphur. The proportion of lime excessively small. (Analysis IX.) 
No, 13. Gray chert from bed somewhat below the last ; shows grayish paste, 
full of obscure organic forms chiefly foraminiferal and molluscan (2). (Analysis X.) 
No. 14. Dark chert with laminated structure, Kilmagar, county Kilkenny, just 
below the Yoredale shales ; shows amorphous or laminated structure, but no appear- 
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