516 Dr. R. H, Traquair—Old Red Sandstone Fishes. 
which I have carefully examined the type, is, to my mind, nothing 
more than a shortened-up and vertically ‘squashed ” specimen of 
O. macrolepidotus. And, as already surmised by Pander, Triplopterus 
Pollexfeni, of McCoy, is certainly an Osteolepis macrolepidotus, so 
crushed that both ventral fins are visible, one of which has been 
mistaken for the supposed single dorsal. 
The beautiful little Caithness fish, minutely described and figured 
by Pander as O. microlepidotus, is certainly a most distinct species, 
whether it be that originally so named by Valenciennes and Pent- 
land or not. It abounds in some localities near Thurso, and there 
is a magnificent set in the Hugh Miller Collection in the Edinburgh 
Museum. 
Thursius, n.gen. Traq. (= Dipterus, Segdw. and Murch. pars, 
Osteolepis, Pander pars, Diplopterus, McCoy pars).—With the speci- 
men figured by Sedgwick and Murchison as a young individual of 
“« Dipterus macrolepidotus,” and erroneously adopted by Agassiz as 
the type of the genus Dipterus, I identify with ease a common 
Thurso species, specimens of which are often seen in museums, 
sometimes labelled <‘‘ Oséeolepis,” sometimes ‘‘ Diplopterus.” By 
McCoy it was considered to be a Diplopterus,' and, strangely enough, 
identified with Agassiz’s D. macrocephalus, while many of the heads 
figured by Pander as belonging to Osteolepis macrolepidotus clearly 
belong either to this, or to a closely allied species. But in reality it 
belongs neither to the one nor the other genus, seeing that to the 
heterocercal tail of Osteolepis it adds the opposition of the two dorsal 
fins to the ventral and anal respectively, as seen in Diplopterus and 
Megalichthys. 
Having failed in my endeavours to construct a descriptive Greek 
name for this genus, I have named it after the locality around which 
its remains are commonly found. ‘Two species are readily distin- 
guishable, and of these the typical one for which we are compelled 
to adopt the name ‘“ macrolepidotus”’ has unfortunately the smaller 
scales. 'The other, possessing scales of a remarkably large size, and 
having the jaws proportionally shorter and broader, I propose to call 
Thursius pholidotus. A species of the same genus, possibly distinct 
from the above, though closely allied to Th. macrolepidotus, is the 
most abundant fish in the flagstones of South Head, Wick, large 
numbers of it having been collected by the late C. W. Peach. 
Diplopterus, Agassiz.—I cannot admit that there is any specific 
distinction between the Dipiopteri of the Moray Frith nodules (D. 
macrocephalus, Ag., and affinis, Ag.) and the common Orkney species 
D. Agassizii, Traill (0. borealis, Ag.), nor can McCoy’s D. gracilis 
be recognized as a “ good” species, for reasons already frequently 
and sufficiently explained. 
Suborder AcCIPENSEROIDEI. 
Family Patzontscipm. 
Cheirolepis, Agassiz.—Concerning Cheirolepis I have the same tale 
to tell. No less than six species of this genus have been described 
1 Pal, Foss. p. 587. 
