The Canadian journal of industry, science and art . Atrypa .—A good deal of uncertainty still prevails ^^^th regard totte proper limitation of this genus. In outward form it agrees withBhynconella, see below, but appears topossess internal calcareous spires, thepoints of which extend into the hollow ofthe smaller or dorsal valve. Fig. 102represents an exceedingly common spe-cies, A, reticularis, of the Upper SUu-rian and Devonian strata, but chieflycharacteristic of the latter. Pig. 102, Bhynconella :—Shell, in general, strongly bi-couvex. Hinge-line,curved ; no area. No internal spires, but i

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The Canadian journal of industry, science and art . Atrypa .—A good deal of uncertainty still prevails ^^^th regard totte proper limitation of this genus. In outward form it agrees withBhynconella, see below, but appears topossess internal calcareous spires, thepoints of which extend into the hollow ofthe smaller or dorsal valve. Fig. 102represents an exceedingly common spe-cies, A, reticularis, of the Upper SUu-rian and Devonian strata, but chieflycharacteristic of the latter. Pig. 102, Bhynconella :—Shell, in general, strongly bi-couvex. Hinge-line,curved ; no area. No internal spires, but in the living species thearms are coiled spirally, the spires pointing downwards and genus ranges from the Lower Silurian into the existing 103 represents a small form, B. plena, very common in the Chazylimestone of the Trenton Group, (Lower Silurian) ; and fig. 105, , a closely related species occurring abundantly through-out the Trenton limestone. In this latter species, the plications.

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Keywords: ., bookcentury1800, bookdecade1850, bookpublishertoron, bookyear1856