1859. ] EOCENE SILUROID FISHES. 205 
sented by figure 10, and it will be seen that all the points mentioned 
as characteristic of the fossil otolith are repeated in this, and it is 
only in outline that there is any real difference. The projection of 
the inner margin marked « (fig. 10 6) isin a depression aud does not 
form a prominent angle as in the fossil (fig. 3 6), and the swelling of 
the outer margin (y) is, in A. gagorides, placed further backwards 
than in the fossil. 
Unfortunately, the otoliths of nearly allied recent species or genera 
are not available for comparison, and consequently we know nothing 
of their specific differences. In the collection of Fish otoliths pre- 
served in the Hunterian Museum of the Royal College of Surgeons 
there are a few belonging to Siluroids, but none of them to genera 
nearly allied to Arius, and they all differ widely from the otolith of 
Arius gagorides. 
The series of otoliths from the Upper Eocene of Barton, pre- 
served in the British Museum, includes many which agree with 
A. gagorides in these main characters which seem to me to be generic, 
and these, therefore, I also refer to the genus Arius. Besides differ- 
ences of size, which in part no doubt are due to age, these otoliths 
present several distinct forms, which I believe will be found to 
represent at least three species, in addition to the skull above 
described. The largest of these (fig. 4) is a little longer and more 
regularly oval than that found in the Barton skull; its lower surface 
is also flatter, and its upper surface is raised into an almost conical 
boss. 
The second form to be noticed (fig. 5) is smaller, flatter, and more 
rounded in outline, having the hinder point ouly slightly produced. 
The third form (fig. 6) is likewise flat and about the same size as 
the one last noticed ; in outline, however, it more resembles that of 
A. gagorides, but the swelling of the outer side (¥) is not thrown so 
much backwards as in that species. 
There is still another form of Arius otolith to which I should 
like to call attention. Among the fossils brought from Madagascar 
by the Rev. R. Baron, and noticed in his paper read before the 
Geological Society (Mar. 6, 1889), were some small otoliths (fig. 7) 
which he had collected in the village of Ankoala, where they 
occurred in some numbers scattered over the surface of the ground. 
These otoliths bear such a close resemblance to some of those from 
the Eocene beds of Barton, that they not unnaturally led to the 
supposition that they also were of Eocene age; but both these 
forms are referable to the living genus Arius, which is a widely dis- 
tributed tropical form, and it seems very probable, therefore, that 
the Anukoala specimens may prove to be of much more recent origin, 
and the peculiar conditions under which they were found seem to 
point to their belonging to a living species. 
We have now to consider the relation which the Barton skull and 
the otoliths above described bear to the specimens referred to Arius 
egertoni and to A, ? bartonensis ; and before doing so I may say that 
I quite agree with Mr. Smith Woodward’ s reference of the cephalic 
plates from Bracklesham to the species d. eyertoni; for their 
