The Canadian journal of industry, science and art . Fig. 98, Pig. 99. mucronattis of the Devonian series. Both are of common hinge-line of the latter is sometimes shorter (as compared withthe height of the shell,) than is shewn in the figure. In our WesternDevonian rocks, several other species occur: as S. duodenarius, witheight or nine rounded ribs on each side of the mesial fold ; S. rari-costatus, with two or three coarse plications on each side of the fold ;S. gregaria, a small species, &c. These are figured and described byMr. Billings in the Canadian Journal, vol. YI. Anot
The Canadian journal of industry, science and art . Fig. 98, Pig. 99. mucronattis of the Devonian series. Both are of common hinge-line of the latter is sometimes shorter (as compared withthe height of the shell,) than is shewn in the figure. In our WesternDevonian rocks, several other species occur: as S. duodenarius, witheight or nine rounded ribs on each side of the mesial fold ; S. rari-costatus, with two or three coarse plications on each side of the fold ;S. gregaria, a small species, &c. These are figured and described byMr. Billings in the Canadian Journal, vol. YI. Another commonspecies of the Upper Silurian series, is S. radiatus. This differschiefly from S. Niagarensis by its finer and more numerous third Niagara species S. sulcatus, has about eight plications oneach side of the mesial fold, crossed by the rough and strougly-pro-nounced edges of the layers of growth. Aihyris:—The shell in this genus has internal spires as in Spirifer,but the hinge-line is curved, and the area is absent or ru
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