484 BAMBLES OF A GEOLOGIST. 



Glyptolepis microlepidotus ; though its state of keeping is 

 such as to render either conclusion an uncertainty. Another 

 of the specimens was that of a fish, still comparatively rare, 

 first figured in the first edition of my little volume on the 

 " Old Red Sandstone," from the earliest found specimen, at 

 a time while it was yet unfurnished with a name, but which 

 has since had a place assigned to it in the genus Diplacan- 

 thus, as the species longispinus. The scales, when examined 

 by the glass, remind one, from their pectinated character, 

 of shells covering the walls of a grotto, a peculiarity to 

 which, when showing my specimen to Agassiz, while it had 

 yet no duplicate, I directed his attention, and which led him 

 to extemporize for it, on the spot, the generic name Ostra- 

 lepis, or shell-scale. On studying it more leisurely, however, 

 in the process of assigning to it a place in his great work, 

 where the reader may now find it figured (Table XI V., fig. 8), 

 the naturalist found reason to rank it among the Diplacanthi. 

 Mr Watt's specimen exhibited the outline of the head more 

 completely than mine ; but the Orkney ichthyolites rarely 

 present the microscopic minutiae ; and the shell-like aspect 

 of the scales was shown in but one little patch, where they 

 had left their impressions on the stone. His other specimens 

 consisted of single plates of a variety of Coccosteus, undis- 

 tinguishable in their form and proportions from those of the 

 Coccosteus decipiens, but which exceeded by about one-third 

 the average size of the corresponding parts in that species ; 

 and of a rib-like bone, that belonged apparently to what few 

 of the ichthyolites of the Lower Old Red seem to have pos- 

 sessed, an osseous internal skeleton. This last organism 

 was the only one I saw in Orkney with which I had not 

 been previously acquainted, or which I could regard as new ; 

 though possibly enough it may have formed part, not of an 

 undiscovered genus, but of the known genus Asterolepis, of 

 whose inner frame-work, judging from the Russian specimens 



