Miscellaneous. 233 On a neiv Subclass of Fossil Birds (Odontornithes). By 0. C. Maksh. The remarkable extinct birds with biconcave vertebrae (Ichthyor-nidfe), recently described by the writer from the upper Cretaceous shale of Kansas *, prove on further investigation to possess some additional characters, which separate them still more widely from all kno^vn recent and fossil forms. The type species of this group, Ichthyornis dispa?', Marsh, had well-developed teeth in both Jaws. These teeth were quite numerous and implanted in distinct sockets ; they were small, compressed, and pointed, and all of those preserved are similar. Those in the lower jaws number about twenty in each ramus, and are all more or less inclined backward. The series extends over the entire upper margin of the dentary bone, the front tooth being very near the extremity. The maxillary teeth appear to have been equally nume-rous, and essentially the same as those in the mandible. The skull was of moderate size, and the eyes were placed well forward. The lower jaws are long and slender, and the rami were not closely united at the symphysis ; they are abruptly truncated just behind the articufation for the quadrate. This extremity, and esjiecially its articulation, is very similar to that in some recent aquatic birds. The jaws were apparently not encased in a horny sheath. The scapular arch, and the bones of the wings and legs, all conform closely to the true ornithic type. The sternum has a prominent keel, and elongated grooves for the expanded coracoids. The wings were large in proportion to the legs ; and the humerus had an extended radial crest. The metacarpals are united, as in ordinary birds. The bones of the posterior extremities resemble those in swimming birds. The vertebrae were all biconcave, the concavities at each end of the centra being distinct and nearly alike. Whether the tail was elon-gated cannot at present be determined ; but the last vertebra of the sacrum was unusually large. This bird was fully adult, and about as large as a pigeon. With the exception of the skull, the bones do not appear to have been pneumatic, although most of them are hollow. The species was carnivorous, and probably aquatic. When the remains of this species were first described, the portions of lower jaws found with them were regarded by the writer as repti-lian t ; the possibility of their forming part df the same skeleton, although considered at the time, was not deemed sufficiently strong to be i^laced on record. On subsequentlj-removing the surrounding shale, the skuU and additional j^ortions of both jaws were brouglat to light, so that there cannot now be a reasonable doubt that all are parts of the same bird. The possession of teeth and biconcave ver-tebrae, although the rest of the skeleton is entirclj-avian in type, obviously implies that these remains cannot be placed in the present * Amer. Journ. of Sci. and Arts, vol. iv. p. 344, Oct. 1872, and vol. v. p. 74, Jan. 1873. 'Annals,' Jan. 1873, j). 80. t Amer. Journ. of Sci. and Arts, vol. iv. p. 406, Nov. 1872.