EXPLANATION OF PLATE 2. D. 



1 CHIROLEPIS OURTUS (M'=Ooy). Natural size ; from the Old Red nodules of Lethenbar. 

 1 a Scale of ditto, from near the tail, outer surface, magnified 24 diameters. 



1 h Ditto, from near the middle of the fish, impression of inner surface, shewing a prominent oval boss 



in the middle, arising from a corresponding articular depression in the scale, magnified 24 diameters. 



2 CHIROLEPIS VELOX (M'^Coy). Natural size ; from the black Devonian flags of Orkney. 



2 a Scale of ditto, magnified 24 diameters. 



3 CHIROLEPIS MACROCEPHALUS (M-^Coy). Natm-al size; from the Devonian flags of Orkney, 



3 a Scale of ditto, magnified 24 diameters. 



4 OSTEOLEPIS BREVIS (M-'Coy). Natural size ; from the nodules in the Devonian rocks of Orkney. 



4 a Scales of ditto, magnified 2i diameters, the two lower scales shewing the external polished and 



punctured surface with their articular margins, the two upper being impressions of the inner surface, 

 to shew the narrow longitudinal sulcus corresponding to the articular ridge on the under side of the 

 scale. 



5 TRIPLOPTERUS POLLEXFENI (M^Coy). Small specimen, natural size ; from the black Devo- 



nian flags of Orkney. 



5 a Scale of ditto, magnified 3 diameters, shewing the polished punctured surface and broad articular 



margin. 



5 h Scales of ditto, natural size, from another specimen. 



6 HOLOPTYCHIUS SEDGWICKI (M^Coy). Natural size ; the dotted restored outlines of the fins 



are from other specimens in the collection ; from the black Devonian flags of Orkney. 



6 a Scales of ditto, magnified 1 h diameters. 



