. Annals and magazine of natural history : including zoology, botany and geology. . Prof. F. M'Coy on some new Mountain Limestone Fossils. 171 sent confined, unless the Pterinea posidoniaformis (M'Coy), (Syn. Sil. Foss. of Ireland, t. 2. f. 10) of the Upper Silurian strata belongs to it. AvicuLOPECTEN (M'Coy), n. g. Gen. Char. Inequivalve, more or less inequilateral, straight, or slightly extended ob- liquely towards the pos- terior side; anterior ear flattened, smaller than the posterior, shai'ply and deeply defined, with a deep notch in the right valve between it and the body of the shell fo
. Annals and magazine of natural history : including zoology, botany and geology. . Prof. F. M'Coy on some new Mountain Limestone Fossils. 171 sent confined, unless the Pterinea posidoniaformis (M'Coy), (Syn. Sil. Foss. of Ireland, t. 2. f. 10) of the Upper Silurian strata belongs to it. AvicuLOPECTEN (M'Coy), n. g. Gen. Char. Inequivalve, more or less inequilateral, straight, or slightly extended ob- liquely towards the pos- terior side; anterior ear flattened, smaller than the posterior, shai'ply and deeply defined, with a deep notch in the right valve between it and the body of the shell for the passage of the byssus; posterior ear slightly pointed, extending about as far as the margin of the shell, defined or not j ligament and cartilage Internal cast of ^t^icwZopec^era. confined to a narrow facet along the hinge-margin, no medial cartilage-pit; muscular impression and paUial scar as in Pecten. It was only on seeing the fine suite of fossils from the dark limestone of liowick, Northumberland, recently presented by the Rev. Mr. Jenkins to Prof. Sedgwick, and now in the collection of the University of Cambridge, that I recognized the characters by which the great bulk of the so-called Pectens of the middle and upper palaeozoic rocks are distinguished from the true Pectens of the more recent formation and present sea. In the present fossils the posterior ear is largest, thus difi'ering in an external character from Pecten and approaching Avicula, an affinity greatly increased by the internal structure exposed by the Lowick (and some Irish) specimens, showing that there is no mesial ligamen- tary pit beneath the beak as in the former genus, but, as in the latter, the ligament is confined to the hinge-margin, while in general form and little or no obliquity of the shell the resem- blance of the species to Pecten is so very striking that most writers agree in placing them in that genus. The discovery of this character fixes the zoological place of numerous carbonifero
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