G8 Miscellaneous. The squamosal has an extraordinary development, and extends on the parieto-quadrate arch, and on the inner side of the temporal fossa on each side of the parietal. The parietal is not so far con-cealed as in IcJithyosauriis, bnt its posterior lateral process may be seen wedged in between the squamosal and the thin, plate-like opisthotic, "which lies external to the supraoccipital on each side. The opisthotic is the parietal of Owen, and the parietal branch of the squamosal is the mastoid of the same author. This branch in Ichthyosawus and Lystrosaurusia continuous with the zygomatic portion of the bone, though another element might liave been originally coossified with it. The posterior 2)ortion of the squamosal is prolonged remarkably ; it is applied to the posterior face of the quadratum, and extends to its articular extremity. The quadratiim is a small bone of a plate-like form, in contact with the squamosal above and the (?) prootic inwardly and anteriorly. Sujrra-stapedial not distinguished. The parietal branch of the squamosal sends down a columella to the pterygoid. The prootic is a distinct though small bone, below and in front of the squamosal. The pre-sphenoid is plate-like, and much as in the Crocodilia. Prof. Cope thought that the Anomodontia, one of the earliest (Triassic) types of Rei^tilia, are one of the best examples of a gene-ralized group among the Vertebrata. Thus the structure of the posterior part of the cranium is largely that of Ichthyopterygia, and partially that of Lacertilia ; of the oral parts of the cranium, the prootic and mandible, of Testudiuata. The vertebral characters are partly those of Ichthyopterygia, and the sacrum and rib-articulations tliose of Dinosauria. -The peculiar presphenoid is characteristic of Crocodilia, and the osseous interorbital scj^tum of llhynchocephalia. The position of the posterior plate of the squamosal in Ichthyo-pterygia and Anomodontia seemed conclusive as to the homology of that element with the bone covering the cartilaginous quadratum in Batrachia Anura, and the osseous quadratum in Urodela and Dipnoi, called tympanique bj' Cuvier, and temporo-mastoidean by Duges. This bone had been already homologized with the pra3operculum of Teleostei by Huxley; and it is thought that its present determination in the Eeptilia established the serial homology of the prfeoperculum of the fish with the squamosal plate of the mammal. — Proc. Amer. Phil. Soc. vol. xi. No. 84. On the Embryology of Limulus polyphemus. By A. S. Packard, Jun. After a detailed description of the embryological history of the TJmuhis, the author concludes that before hatching it strikingly re-sembles Trinudeus and other Trilobites, a conclusion to which the whole account points. The Trilobites are therefore lower than the Xiphosura ; the two groiips should, on embryonic and structural grounds, be included perhaps in one order ; and the former should therefore be removed from the neighbourhood of the PhyUopods and placed immediately next to Xiphosura. The organization
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