508 Dr. R. H. Traquair—Old Red Sandstone Fishes. 
honour of the distinguished French ichthyologist. As a synonym it 
is also necessary to include Polyphractus platycephalus, Ag., which 
was long ago shown to be a Dipterus by H. Miller. One species, 
however, exceedingly distinct from D. Valenciennesii, may here be 
briefly described. 
D. macropterus, n.sp. Traq.—Distinguished from D. Valenciennesia 
by the long base and broad rounded contour of the second dorsal 
fin, and by the thinness of the scales, which permit the outlines of 
the internal skeleton to be seen through them. The other fins are 
as in D. Valenciennesii, the pectorals and ventrals being beautifully 
“ archipterygial” in their contour. 
Lower Old Red Sandstone, John o’Groats, Caithness, Edinburgh 
Museum, collected by the late C. W. Peach. 
Order GANOIDEI. 
Suborder PLacoDERMATA. 
Family AsTEROLEPIDE. 
Asterolepis and Pterichthys.—There can be no doubt that Asterolepis, 
Eichwald, is prior to Pterichthys, Agassiz, and if Pander were right 
in maintaining the identity of the two genera, it would be hard to 
deny the preference to the first of these names. But Beyrich,} 
Lahusen,’ and Zittel,® accepting Sir Philip Egerton’s view that the 
arms in Pterichthys were articulated to ‘‘thoracic”’ plates, distinct 
from the anterior ventro-laterals, have founded a diagnostic mark on 
this supposed peculiarity, as such ‘‘thoracic”’ plates certainly do not 
exist in the Russian Asterolepis. But just as little do they exist in the 
British Péterichthys, as an examination of hundreds of specimens has 
absolutely convinced me that the pectoral limbs were articulated here 
precisely as in Asterolepis. A valid generic distinction may, how- 
ever, be found in the mode of articulation of the anterior median 
dorsal plate. According to Pander this plate overlaps both the 
anterior and posterior ventro-laterals, whereas in Pterichthys, though 
it overlaps the former, it is itself overlapped by the latter. These 
facts regarding the body-plates of Pterichthys were long ago known 
to Hugh Miller; it is interesting to add that the general structure 
of Pterichthys, including that of the head and arms, is very much 
closer to that of Asterolepis than of Bothriolepis, some of whose 
species,—namely, hydrophilus, Ag., major, Ag., and macrocephalus, 
Egert., have been included in Pterichthys. 
Asterolepis maximus, Ag. sp.—The large Asterolepid occurring in 
the Upper Old Red Sandstone of Nairn (Seabank and Kingsteps), 
a fragment of whose anterior median dorsal plate was figured by 
Agassiz as “ Coccosteus” maximus, and afterwards supposed by Hugh 
Miller to belong to “ Pterichthys”” major, seems to me to be referable 
to Asterolepis, as the anterior median dorsal plate most undoubtedly 
overlaps both anterior and posterior dorsal-laterals. I have now got 
1 «Ueber einen Pterichthys von Gerolstein,” Zeitschr. deutsch. geol. Gesellsch. 
1877, p. 754. 
* «Zur Kenntniss der Gattung Bothriolepis, Eichw.,” Trans. Imp. Min. Soe. 
St. Petersburg. 1879. 
3 «* Handbuch der Paleontologie,” vol. iii. pt. 1, pp. 153-157. 
