1889. ] ON SOME EOCENE SILUROID FISHES. 201 
3. A Contribution to the History of Eocene Siluroid 
Fishes. By E. T. Newton, F.G.S., F.Z.S. 
{Received March 14, 1889.] 
(Plate XX1.) 
The pectoral and dorsal spines of Siluroid fishes from Brackle- 
sham, which were referred to the genus St/urus by Dixon (2'), have 
recently been studied by Mr. A. Smith Woodward (12), who has 
shown the improbability of these remains belonging to the temperate 
genus Si/urus and the close relationship existing between them and 
the widely distributed tropical genus Avius. In addition to the 
spines and pectoral arch, named by Dixon Silurus egertoni, Mr. 8. 
Woodward has called attention to several other specimens, some 
from the Upper Eocene of Barton, preserved with the types in the 
British Museum, among which are bones of the skull and notably 
some large and characteristic supraoccipitals, one of which he 
figures; these he also refers to Arius egertoni. Some smaller spines 
with a double curvature, from Barton, he places in a new species, 
Arius (2) bartonensis. 
The Museum of Practical Geology now possesses the greater part of 
askull from the Eocene beds of Barton (Plate X XI. figs. 1, 2,3), which 
confirms in a most satisfactory manner Mr. S. Woodward’s reference 
of the Eocene Siluroids to the genus Arius. The skull is somewhat 
crushed, but the bones are still in position, and by careful manipu- 
lation both the upper and under surtaces have been exposed. The 
ethmoid, prefrontals, and part of the supraoccipital are wanting, 
and on the right side the temporal region is broken, but on the lett 
only one of the temporal plates is lost. 
All the Lones of the upper surface, which are preserved, are 
ornamented with rounded granules, and these in nearly all cases 
radiate from an ill-defined ceutre towards the margins of the bone. 
No distinct sutures can be seen, but the ornamentation being less 
strongly marked towards the edges of the bones, the boundaries can 
be fairly well made out; the dark lines in the figure indicate these 
boundaries, which agree in the main with the positions of the sutures 
in the recent specimen with which it has been compared. 
The frontals ( fr.) oceupy the anterior part of the specimen; they 
are narrow posteriorly and meet each other in the middle line for 
about half their length. The median point of the supraoccipital 
projects for a short distance between their hinder extremities. An- 
teriorly a wide and deep depression occupies the median portion of the 
frontals, and at the bottom of this depression a long cleft separates 
their inner margins, Each bone is in front divided into two parts, 
the outer of them no doubt joined the prefrontal and the inner the 
ethmoid, as in the recent Arius. 
Behind and on the outer side, each frontal joins a plate (sp.ot.) 
* These numbers refer to a list of works given p. 206. 
