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Show 1889.] MR. A. S. WOODWARD ON BUCKLANDIUM DILUVII. 209 fused together, and the superficial tubercular ornament is so sparse and exhibits so indefinite an arrangement, that not even an approximate determination of the original sutures can be attempted. The only noteworthy feature is the complete absence of tubercles upon a narrow longitudinal area (fo.) in the median line commencing somewhat in advance of the supraoccipital, gradually widening in front, and evidently passing into an elongated frontal fontanelle. The hinder margin of the cranial roof is not much broken, and so displays the posterior extent of the supraoccipital ; but the only portion of the lateral margin is the superiorborder of the right orbit (orb.), which is interesting as showing the forward position of the eye. Seen from beneath, a kind of sudden thickenino* of the roof-bones is observed to commence at a short distance behind the orbit, producing the appearance of a deep fossa anteriorly ; but no precise information can be obtained as to the characters either of the brain-case or the otic bones. The displaced base of the skull and the anchylosed vertebrae are too imperfect for description ; but the basioccipital and parasphenoid appear to be narrow (fig. 3, ps.), while the side-walls of the skull rapidly slope upwards. At the union of the basioccipital with the anterior vertebrse (ar.) there is a broad downwardly-directed angular process of bone ; and the furrow along the inferior aspect of the anchylosed centra (v.) is shallow. The posttemporal bone (figs. 1, 2, pt.), though firmly fused with the cranium, is sharply separated by suture from the anterior upper angle of the clavicle ; it is broad throughout its length, gradually expanding towards its distal articulation. The pectoral arch is best preserved on the right side, though even here only fragments of the ornamented dermal plate of the clavicle remain ; and the articular facettes for the spine, equally with the infraclavicular plates, are mutilated beyond precise recognition. The clavicular element (cl.), evidently comprising, as usual, the supraclavicle of ordinary Teleosteans, is about twice as deep as broad and does not taper, but rather expands inferiorly. Its lower boundary is arched and seems to have projected over the base of the pectoral spine; a thin flat plate of bone extends directly inwards from the lower half of its curved front margin ; and a more robust bony plate similarly proceeds inwards from the lower half of the hinder margin and bulges postero-inferiorly in such a manner as to suggest its being an upward extension of the infraclavicle (i.cl.). Such being the characters of the fossil, it obviously resembles the skull and pectoral arch of recent Siluroids with sufficient closeness to be placed in that great group of Teleostei. Without a knowledge of other portions of the fish, however, it is impossible to determine the precise affinities of Bucklandium in the usual manner. It must suffice merely to compare the specimen with the skulls of various recent genera, aud thus arrive at an approximate determination. So far as the writer has been able to observe, the London Clay genus most closely approaches the living Auchenoylanis of the Nile and West-African rivers ; and a reduced side view of the head, ante- |
