104 J. E. Lee — A Pteraspidean Plate from the Eifel. 



II. — Notice of a Pteraspidean Cephalic Plate from the 



Devonian Beds of Gerolstein in the Eifel. 



By John Edward Lee, F.S.A., F.G.S. 



(PLATE IIL) 



LAST Autumn, on our way to St. Cassian and the Dolomites, 

 we remained for two or three days in the Eifel. The little 

 town of Gerolstein is well known to all geologists. Mr. Winter, 

 one of the inhabitants, who pays considerable attention to the natural 

 history of the place, was kind enough to present me with a nodule 

 which, though apparently it is very insignificant, yet, on further 

 examination, seems of great interest ; it contains, in fact, part of the 

 scale of a Pteraspidean. Any one who has worked amongst the Old 

 Eed Sandstone fishes of Monmouthshire and Herefordshire will at 

 once recognize many of the characteristics of the Pteraspidean scales. 



There are, however, some peculiarities in the scale found in this 

 apparently insignificant specimen, which are probably worth placing 

 on record until better specimens are found, which should at once be 

 placed in the hands of an expert ; there may possibly be characters 

 sufficiently different from the usual structure to form a new genus. 



It is well known that the scute or dorsal plate of the Pteras- 

 pideans, as yet known, is composed of three layers ; the lower one 

 is called by Professors Huxley and Lankester the nacreous layer ; it 

 does not show mucli organization under the microscope, but still a 

 few vessels may be distinctly seen passing through it. Above this 

 is what may be called a layer of "honeycomb" structure, the walls 

 of which, when highly magnified, are found to be composed of a large 

 number of very thin plates. This character is very well seen in 

 sections from the Monmouthshire Pteraspideans. A small portion of 

 one is given (Plate III. Fig. 1). The Looe and Polperro specimens 

 (Scaphaspis) are very nearly the same, but the structure of the walls 

 is not so. apparent; probably this difference is caused by greater 

 mineralization. Fig. 2 is part of a sketch of one of these sections 

 from Polperro. These two sections are merely explanatory of the 

 normal structure of the middle or honeycomb layer. The upper, or 

 what has hitherto been considered the outer, layer is black in colour, 

 and made up chiefly of parallel lines, almost exactly like those of 

 the corrugated sheet iron roofs now in common use. Fig. 3 will 

 give an idea of a small portion of this coat from a specimen from 

 Polperro. 



In the specimen under consideration from the Eifel (Plate III. 

 Figs. 4 and 5) there appear to be some peculiarities. In the first 

 place, the nacreous layer seems to be absent, and though, as has been 

 observed by a leading paleontologist, this may be accounted for by 

 supposing that it has perished, there is still a greater peculiarity 

 which can hardly be explained in this manner ; for apparently the 

 black corrugated portion is not on the outside, but (at least in one 

 instance) lies between two of the honeycomb layers. Fig. 6 is a 

 side-view, and Fig. 7 is a much magnified view of what appears to 

 show that in this Eifel scale there are two if not three " honey- 



