The Annals and magazine of natural history . s is very much less soluble in acids than calcite, so that itis left as a residue on dissolving limestone in dilute hydro-chloric acid. The silicic acid which dissolved and replacedthe calcic carbonate would therefore act with greater difficultyon the dolomite, and, indeed, would in all probability have noaction upon it at all; and so, while the mass of the limestoneunderwent silicification, the rhombohedra of dolomite wouldremain unaltered in the midst of the chert, just as we nowfind them. That the formation of the chert continued, if it did not c
The Annals and magazine of natural history . s is very much less soluble in acids than calcite, so that itis left as a residue on dissolving limestone in dilute hydro-chloric acid. The silicic acid which dissolved and replacedthe calcic carbonate would therefore act with greater difficultyon the dolomite, and, indeed, would in all probability have noaction upon it at all; and so, while the mass of the limestoneunderwent silicification, the rhombohedra of dolomite wouldremain unaltered in the midst of the chert, just as we nowfind them. That the formation of the chert continued, if it did not com-mence, some time subsequent to the formation of the limestoneis proved by a curious fact observable in the section of coralshown in the centre of the section represented in fig. 1 ofProf. Hulls plate. Some of the vesicular spaces at the edgeof this are completely lined by crystals of calcite (dog-toothspar) which has not undergone silicification, while the interiorof the spaces is occupied by crystalline grains of quartz(fig. 2). Fig. Part of section of coral from chert (fig. 1, pi. iii. Hulls paper) : Q e, ex-ternal wall, consisting of radiating crystalline fibres of quartz ; S,septum; CJ calcite lining marginal vesicle; Q i, quartz within thevesicle. ( X 60 diam.) It is clear that the coral had been dead and exposed to the# Bull, de lAcad. roy. Belg. 2« ser. t xlvi. On Dredging off tk\ South Coast of New England. 143 action of surrounding wate^long enough for a deposit ofcalcite to be formed within the marginal vesicles before theinfiltration of silica occurred. Of the section of chert labelled C 41 I could make butlittle; it appeared to contain clastic granules of quartz. XIV.—Recent Dredging by the United-States Fish Com-mission off the South Coast of New England, with someNotice of the Crustacea obtained. By S. I. Smith. The United-States Commission of Fish and Fisheries, underthe direction of the Commissioner, Professor Baird, withheadquarters at Newport, Rhode
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