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Show 1897.] DR. R. H. TRAQUAIR ON PALcEOSPONDYLUS GUNNI. 315 had been sent to him by Mr. W. T. Kinnear, of Forss near Thurso. His interpretation of this specimen, along with a magnified figure, will be found in a paper entitled " Is Palceospondylus a Cyclostome ?" published in the ' Transactions of the N e w York Academy of Sciences ' for 1896 (vol. xv.). Here (pp. 101, 102) Dr. Dean states that in this specimen " a dusky band may, on either side, be traced tailward from the region of the ' auditory capsules.' These bands when examined with a glass are found to resolve themselves into a series of ray-like structures arranged transversely to the axis of the body, but slightly inclined backward They cannot be said to definitely take their origin from post-occipital plates, although they certainly appear to, and there is a suggestion that the right occipital plate has been formed of metameral elements. The band of ray-like structures continues, however, caudad of the pectoral region, traceable backwards to the region of about one-half tbe length of the vertebral axis Negative as well as positive evidence, accordingly, indicates that these fin-like rays w?ere concerned with the presence of paired fins. If this be true, is Palceospondylus to be regarded as a Marsipobranch ? " The paper finishes with an arrangement in tabular form of the evidence for and against the marsipobranch affinities of Palceospondylus, from which it would appear that he still looks upon the cirrated opening as a " mouth," and that he thought the post-occipital plates may " well represent basalia of pectoral fins." After all, the only conclusion to which the author comes is that "the position of the fossil, if not to be regarded as marsipobranchian, is certainly undefinable." As Dr. Dean has been so extremely kind as to send his specimen over to this country that we may examine it for ourselves, I am enabled by this act of courtesy on his part to offer a few words as to my interpretation of the appearances presented by it. It belongs to the class of specimens which may be designated as moderately good. The black substance of the skull and vertebrae is fairly well preserved, but the surface is gone. The post-occipital plates are not well preserved, so that the " suggestion " as to one of them being formed of " metameral elements" is absolutely without value. The vertebral centra are in pretty good condition, some of them in front being so turned up as to show their ring-like conformation with great distinctness. These are the parts seen on the specimen; if there were anything more we should expect it to be preserved in the same way. O n examining the specimen with a low power, taking care to turn the head towards the light, we see the dusky band clearly enough on the right1 side, though it is scarcely perceptible on the opposite one ; and we also see the appearance of this band being divided into transversely directed ray-like bodies. Then if we turn round the fossil so that the light may strike on the vertebral column from the convex side, then the dusky band with its ray-like markings at once disappears-but not so the black substance of 1 In reality the left side, as the specimen, as usual, lies on its back. 21* |