548 



PKOP. E. W. CLA.YPOLE ON THE STEUCTUKE 



venes the opinion that has previously been universally held, is 

 always regarded with a certain measure of doubt till confirmed by 

 the finding of further specimens by other workers. In his own 

 words, as printed in the ' Canadian Eecord of Science ' for 1886, 

 we read : " The author is not aware that the existence of a ventral 

 shield has hitherto been observed in any Pteraspidian fish, although 

 it is well known to exist in the large Devonian Placoderms." 

 Mr. Matthew here uses the same argument as that employed by 

 Schmidt (which indeed must have occurred to the mind of any 

 palaeontologist) in order to render more probable, or, we may 

 rather say, less abnormal, the- new view concerning the defensive 

 armour of the Pteraspids. 



Y. Von Alth's Specimen and Tnteepeetation. 



We come now to the paper of Yon Alth published in 1886, 

 the same year in which Matthew announced his Diplaspis, but 

 neither author was aware of the work of the other. This writer 

 had already in 1874 published descriptions of ten species, belonging 

 to the genera Pteraspis, Cyatliaspis, and Scaphaspis, from the Upper 

 Silurian strata of Podolia. But in 1883, during an expedition in 

 search of fossils, he came upon a specimen of so peculiar a character, 

 that after careful removal of as much of the matrix as was possible, 

 he could reach no other conclusion than that it showed a Pteraspis 

 and a Scaphaspis together exactly as in Kunth's specimen, and afforded 

 fresh and incontrovertible proof of their relationship. This fossil 

 he made the subject of a communication (in Polish) to the Cracow 

 Academy of Natural Sciences,^ and of another (in German) to the 

 ' Beitrage zur Palaeont. Oesterr.-Ung.' ^ 



The evidence of this new find, as developed and set forth by 

 Yon Alth, was so convincing, when added to the previous discovery 

 of Kunth, that it may fairly be said to have established an epoch in 

 the history of these fossils, for it was scarcely possible that any 

 doubt could longer remain in an unbiassed mind. 



Yon Alth candidly acknowledged in his paper that he had till 

 the discovery of this specimen strongly opposed, with Lankester, 

 the new view put forward by Kunth and defended by Schmidt : — 

 " In meiner oben erwahnten Arbeit liber die palaeontologischen 

 Gebilde Podoliens und deren Yersteinerungen babe ich ebenfalls 

 die Ansicht vertheidigt dass Pteraspis und Scapliaspis ganz verschie- 

 denen Thierformen angehorten." But he frankly avowed the change 

 of front caused by his own discovery, and was quickly followed in 

 the same movement by Lankester,^ who wrote : " The specimen 

 described and figured by Yon Alth leaves no doubt in my mind as 

 to the interpretation of Scaphaspis adopted by him." 



The results of Yon Alth's paper may also be seen in Mr. Smith 

 Woodward's new ' Catalogue of the Possil Fishes in the British 



^ Verhandl. d. Krakauer Akadem. d. Wissensch. vol. xi, p. 160, &c. 



2 Op. cit. Band v. (1887) p. 61. 



3 See ' Nature,' vol. xliii. p. 578, April 23rd, 1891. 



