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Show 316 DR. R. H. TRAQUAIR ON PALcEOSPONDYLUS GUNNI. [Mar. 16, the rest of the fossil. Then if we examine the specimen further with a higher power, w e should find that these striated markings contain not a particle of organic tissue-they are mere shadows • so that Dr. Dean's expression " a series of ray-like structures" is surely inapplicable to them, and the figure of them which he gives in his paper is quite misleading. There is no doubt that the outer margin of the " dusky band," lettered " marginal body-wall" in Dr. Dean's figure, represents a slightly elevated ridge on the stone, and that the " ray-like structures " are slight furrows brought into relief only when the specimen is so held that the light brings out their shadows. The next thing to be observed is that these ray-like shadows are not limited to a position internal to the line B . W . in Dr. Dean's figure, but extend beyond it towards a second longitudinal line parallel with tbe first, and there is even an indication of a third one. Furthermore, if w e examine the whole surface of the stone, carefully turning it so that the light may fall on it from various directions, w e shall be surprised to find indications of similar striated markings cropping up here and there quite apart from the fossil. Consequently m y belief has come to be, that these markings, considered by Dr. Bashford Dean to be rays of a pectoral fin, are petrological and not palseontological in their nature-that they are, in fact, inorganic and have nothing to do with the fossil itself, which stands clearly out from them in its deep black contour of calcified cartilage. But even if these markings were organic and belonged to the specimen of Palceospondylus with which they are associated, Dr. Dean's interpretation of them is still inconsistent. For if the outer edge of his " dusky band," marked B.W. in his figure, be really the " marginal body-wall," then his supposed " radial-like supports (of paired fins)," which pass inwards from this line, must, according to his o w n theory of the paired fins, be " basals " and not "radials." Nevertheless he also says of the post-occipital plates that they " might well represent basalia of pectoral fins." Apparently still under the conviction that the cirrated ring which I have interpreted as nasal is oral in its nature (how a mouth could go directly into the front of the cranium I fail to see), he leaves the nose, upon which I have naturally placed the principal weight, altogether out of consideration in his summary of characters for and against the marsipobranch affinities of Palceospondylus. A n d note his remark : " Moreover it is possible that the ventral ' cirrhi' are displaced structures from the cranial region, as one of the specimens examined by the present writer seems to indicate." Of course these " ventral cirrhi," namely the cirri on the ventral half of the nasal ring, are cranial structures, and I certainly did not describe them as anything else! It is really a matter for regret that Dr. Dean did not, as it would seem, read m y paper with a little more care. Although Dr. Dean admits that the caudal fin of Palceospondylus is "essentially marsipobranchian," |