724 DR R. H. TRAQUAIR ON 



colour, sometimes with a tinge of purple, moderately hard, and splitting very evenly 

 into layers, the surface of which has a ' certain silky appearance, due apparently 

 to the presence of excessively minute scales of mica. The fossils are entirely converted 

 into hard iron pyrites, and are, when found in the quarry, invariably covered with a 

 layer of matrix, which has to be removed by the expenditure of much time and patience, 

 the instruments used being pointed knives and a brush of fine brass wire, which has the 

 advantage of being harder than the slate, but softer than the pyritised fossils. When 

 properly prepared, these fossils, both invertebrate and vertebrate, form extremely 

 striking and beautiful objects, their drawback being that their pyritised condition 

 renders them quite unavailable for microscopic examination. Occasionally the pyrites 

 is not confined to the substance of the organic remains themselves, but, at places, forms 

 also a layer over their surfaces, which cannot possibly be cleaned off, and by which the 

 appearance of the fossils, as well as their value as specimens, is much impaired.* 

 Hitherto I have only seen this condition in the case of fishes from Gemunden. 



Another point to be noticed as regards the condition of the fossils is the deformation 

 to which they have mostly been subjected. In this way bilaterally symmetrical organ- 

 isms, such as Trilobites and fishes, are seen to be almost invariably obliquely disturbed, 

 one side being pushed in advance of the other, as is well shown in the specimens of 

 Drepanaspis represented in Plates II. , III., and IV. 



It is perfectly clear from the contained invertebrate fossils that the Hunsriick 

 slates are of marine origin, and consequently that their " mailed " fishes were inhabitants 

 of the sea. This is, however, not strange when we remember that " mailed " fishes 

 (Pterichthys, etc.) also occur in the Middle Devonian Limestones of the Eifel, in 

 company with such purely marine fossils as crinoids and brachiopods. Strange it is, 

 however, that, so far as I can ascertain, it is only in one locality, namely Gemunden, 

 that fish remains have been found in these slates, while, on the other hand, Bundenbach 

 is famed for the variety and beauty of its crinoids and starfishes. 



It is also noteworthy that at Gemunden the overwhelming majority of the fish- 

 remains belong to one species, namely, Drepanaspis Gemiindenensis of Schliiter ; the 

 fact being that of the four other species obtained, each is as yet represented only by a 

 single unique specimen. This reminds us of the condition in the Upper Old Red Sand- 

 stone at Nairn in the North of Scotland, where almost all the fish-remains (tolerably 

 abundant in certain parts of the rock) belong to one species, namely, Asterolepis 

 maxima, Agas., though the proportion of relics of other species is certainly higher 

 than at Gemunden in relation to Drepanaspis. 



My attention was first drawn to these fishes twelve years ago by Mr Sturtz, of Bonn, 

 through whose agency, and also through that of Dr F. Krantz, I have succeeded in 

 getting together an excellent collection for the Edinburgh Museum of Science and Art. 

 To Professors Branco and Jaekel I have to express my sincere thanks for permission to 



* See Plate I. fig. 1 and Plate V. fig. 2, in which the scales on the side of the tail pedicle of Drepanaspis are in this 

 manner concealed. 



