344 DR. BASHFOBD DEAN ON rAL.IOSPONDXLCS GUNNI. [Apr. 19, 



was described tabulated also the reasons for and against the 

 alliance of Palceospondylus with the C3'clostomes, maintaining 

 finally that the sole character directly favourable to this alliance 

 was the ring-shaped opening at the head terminal, and that even 

 this evidence was far from convincing. 



Some of these objections, however, were shortly answered by 

 Dr, Traquair\ the describer of the fossil and the vigorous 

 supporter of its supposed cyclostomian affinities. The debatable 

 specimen had been sent to him at Edinburgh ; but it had not con- 

 vinced him that the radial-shaped markings were other than petro- 

 logical. He criticises, furthermore, several points in terminology, 

 and, although he does not consider the balance of evidence as being 

 against the marsipobranchian features, feels himself justified in con- 

 cluding that the question of the affinities of Palceosj^ondi/lus is left 

 where it was after he had written his last paper on the subject: that 

 is that, according to his interpretation of the fossil, there seems no 

 escape from the conclusion that it must be classed as a marsipobranch. 



The purpose of the present paper is to re])ly to the criticism of 

 Dr. Traquair and to emphasize the non sequitur of his general 

 conclusions. The latter purpose is the more interesting, for to 

 retain Palceospondyhis even provisionally in the position of a Devo- 

 nian cj^clostome will certainly, on such slender evidence, prove of 

 little value, if not of actual harm, to phylogenetic studies. 



The answer to the criticism of Dr. Traquair may be arranged : — 



(I.) As to the " petrological " nature of the supposed fin-supports, 

 and (II.) as to the matters of terminology. 



(I.) The evidence that the markings first described by me are 

 not petrological has in part been furnished me most generously 

 by Dr. Traquair himself ; for during a recent visit to Edinburgh he 

 permitted me to examine the material of Palceospondylns both in 

 the Museum of Science and Art and in his private cabinet ; and a 

 specimen of the latter he has even loaned to me for further study — 

 kindnesses which I acknowledge gratefully. Among these spe- 

 cimens were two or three which showed distinct traces of the 

 questionable markings as first described, in the same position, of 

 the same general shape and size. That these markings re-occur 

 so similarly seems to me conclusive evidence that they must be 

 interpreted as structures of the fossil. But it will be objected 

 that these markings have retained no organic matter, " mere 

 shadows," as Traquair expresses it, due to favourable illumination. 

 Be this granted in every case but the first, where I am not satisfied 

 that all traces of tissue have been w eathered out : yet this ob- 

 jection is by no means fatal. For in numerous specimens of Palceo- 

 spondylus the markings of the tips of the caudal fin-rays are equally 

 lacking in organic matter, " mere shadows/' best to be seen with 

 an oblique hght, — yet no one will doubt that these ray-shaped 

 shadows represent structures of the fossil. The writer has in 

 mind entire specimens of Palceospondylus in Mr. Kinnear's 

 collection which have been intentionally " weathered out," in which 

 nothing remains but the " shadows " of head, vertebrae, and tail 1 

 ' Proc. Zoo!. Soc. 1897, pp. 314-317. 



