J. E. Lee — A Pteraspidean Plate from the Eifel. 105 



comb " layers separated by black lined layers. It will be seen that 

 though in almost every case the black corrugated layer has dis- 

 appeared, yet it has left its marks upon the surface of the corrugated 

 layer. My friend Mr. Pengelly, who, in fact, knows more of the 

 Polperro Pteraspideans than any one else, before he saw the speci- 

 men, suggested that the repetition of the honeycomb layer might 

 possibly be accounted for by one scale having been washed into 

 anothei", so that, in fact, the specimen consisted of two scales instead 

 of one ; but, if so, what has become of the nacreous layer ? and 

 in fact, a careful examination of the portion drawn will probably 

 convince the observer that it consists of one and not of two scales. 

 It may possibly be said that the scale has been broken up and one 

 part as it were faulted up and pushed over another part ; but though 

 there may be some probability in this explanation, yet it seems to 

 me that, after a careful examination of the specimen, this idea will 

 be abandoned. Figs. 4 and 5 give a sketch of the general 

 appearance of the two sides of the nodule. 



It may be an abortive or " monster " scale, and so not entitled to 

 much consideration ; but still it is as well to place such abnormal 

 structures on record. 



As the specimen under consideration is the only one as yet dis- 

 covered at Gerolstein, it has not been thought desirable to deteriorate 

 it by repeated attempts to make a section of the " honeycomb " struc- 

 ture. It may be well to mention that on account of the tendency 

 of this structure to disintegrate under the operation of grinding, it 

 is extremely difficult to obtain microscopic sections of it. The 

 section of which a portion is drawn. Fig. 1, was only obtained after 

 fully twenty failures. Not more than three or four were attempted 

 from this Eifel nodule, and the thing was then abandoned, lest the 

 specimen should be spoiled, which probably would have been the 

 case, had a larger number of sections been tried. 



Note. — Since writing the above, Mr. Pengelly has kindly allowed 

 me to see his splendid specimen from Looe. My first impression 

 was that of extreme regret that there is no published drawing of 

 such a beautiful specimen, and I must confess that Mr. Pengelly's 

 explanation of the repeated " honeycomb " layers seems perfectly 

 correct as far as his specimen is concerned, for there is not only a 

 very thin layer of slate between these layers, but in one place there 

 is also the indication, if not more, of the nacreous layer ; but the case 

 seems very different in the Gerolstein specimen, as neither the 

 separating slate nor the nacreous layer seems at all visible in it. — 

 J. E. L. 



EXPLANATIOISr OF PLATE III. 



Fig. 1. Highly magnified section of Scaphaspis (Pteraspis) Lewisii, Old Eed 



Sandstone, Maindec, Monmouthshire, showing honeycomb structure. 



Magnified 20 times. 

 ,, 2. A similar section of Scaphaspis cornubicus, Devonian, Polperro, 



Cornwall. Magnified 6 times. 

 ,, 3. Magnified view of the corrugated surface layer of Sc. cornubicus, 



Polperro. 



