Fossil Fishes of the Upper Old Red Sandstone. 377 
One additional genus and species (Psammosteus tesselatus) 
must now be added to the Nairn list, while it now seems 
clear that at least one species (Holoptychius decoratus, 
Eichwald) extended into the Elgin beds. 
Psammosteus tesselatus, sp. nov., Traquair. 
[Plate XI. Figs. 1 and 2.] 
Shield shallow boat-shaped, resembling in form that of 
P. Taylori, but its substance is thin in comparison. Outer 
surface fretted with very closely placed stellate tubercles, 
polygonal, and often irregularly so, in form, their edges 
marked by exceedingly minute serrations. 
No division of the outer layer into polygonal areas is 
observable, as in the case of P. Taylori, Traq., and some 
examples of P. paradoxus, Ag. 
In the course of the past summer, Mr Taylor sent me the 
beautiful fragment now in the Edinburgh Museum, and of 
which a portion is represented in Pl. XI., Fig. 1, magnified 
two diameters, while the external sculpture, enlarged still 
further to eight diameters, is shown in Fig. 2, On examining 
it, 1 at once remembered two fish-plates which I had col- 
lected some years previously at Nairn (Kingsteps Quarry), 
and on re-examination I found that one of them presented 
the outline of a nearly entire Psammosteus shield, though the 
outer layer was unfortunately quite gone. The other, a 
portion of a larger plate, showed the smooth inner surface, 
but on raising a portion from the matrix, I found on the 
outer surface clear evidence of the same minute mosaic-like 
tuberculation, shown much more perfectly on the specimen 
sent to me by Mr Taylor. 
In general aspect the ornament in this species resembles 
very considerably that in the Russian species P. paradoxus 
and P. arenatus, but the tuberculations are not so pro- 
minently rounded, while their marginal serrations are 
much finer. 
