400 Proceedings of Royal Society of Edinburgh. [sess. 
As already mentioned, I have seen no such dentition either in 
Gonatodus or in any other palseoniscid fish, and consequently I have 
considered it advisable to constitute the new genus, Drydenius, for 
this little fish. The name is taken from the Yale of Dry den, which 
is in close proximity to the ironstone mines of Borough Lee and 
Loanhead. Type specimens in the Edinburgh Museum of Science 
and Art. 
Eurynotus crenatus , Agassiz. — The original specimen of E. fim- 
briatus , Ag., from Wardie, in the Oxford Museum, is a very poor 
fragment, upon which no specific characters distinguishing it from 
E. crenatus can really he founded, especially if one takes into 
account the enormous number of other specimens of the genus from 
the Scotch Lower Carboniferous rocks which have been collected 
since Agassiz wrote the Poissons Fossiles. These specimens show 
very great differences in many respects; but the result of my 
puzzling over them for years is that, with the exception of a peculiar 
form from Loanhead, all must be referred to the same species, 
namely, E. crenatus , Ag. In some cases the scales are comparatively 
smooth, in others more ornamented ; in some the crenation of their 
edges in the dorsal region is extremely coarse, in others this character 
is not so marked. With regard to the fin-rays, the same remarks 
apply which I made in the case of Elonichthys nemopterus, namely, 
that in young specimens these are more slender and the transverse 
joints more distant than in adults, in which also there is no fixed 
condition as regards this particular. In many instances the rays of 
the dorsal fin are serrated posteriorly, but I cannot venture to found 
a species on this. 
Eurynotus microlepidotus , n. sp. — Characterised by the small size 
of its scales and the large dimensions of its fins. C.L., Loanhead. 
Type specimens in the collection of the author. 
Cheirodus crassus, n. sp. — Scales with a relatively coarser ornament 
than in Ch. granulosus , Young ; internal rib or “ lepidopleuron,” 
not nearly so distinctly marked off ; C.Z., Abden. The same scales 
occur at Beith, Ayrshire, associated with dentary plates referable to 
Cheirodus. Type specimens from Abden in the Museum of Science 
and Art. From Beith, in the collection of Kobert Craig, Esq., 
Langside, Beith. 
