46 
very prominent, forms a triangle, tlie height of nliich is almost equal to the 
base. The miclclle rib is twice the size of the adjoining ones, and dilates 
gradually towards the margin without hifurcating. The rib which adjoins the 
thorax becomes a little larger than the others towards the end. The six 
intermediate ribs are similar to one another, and are separated by narrow 
furrows which near the edge are not a third the width of them. 
According to Barrande the doublure of the test only extends over two- 
fifths of the distance between the edge and the rudiment of the axis. I have 
been able to satisfy myself that in the Australian sj)ecimen it extends right to 
the rudiment of the axis. This is the only difference I have been able to 
determine. 
Dimensions . — Length of pygidium, seven; breadth, ten millimetres. 
Horizon and Localities . — In Bohemia this species is characteristic of 
the limestone called E. by Barrande, which forms the base of the Upper 
Silurian beds ; it is found near Beraun and in several other localities. Mr. 
Clarke has collected it at Boree Cavern in a mottled limestone of white, grey, 
and red. 
2. Bronteus goniopeltis, L. G. de Koninck. 
PL I, fig. 10. 
The shape of tlie pygidium in this species is rather peculiar, so that it 
is easy to distinguish it from those of all its congeners at present known. 
The outline is parabolic and broader than long, the median portion of the line of 
articulation with the thorax forms almost the third of its extent, and is straight, 
while the lateral portions are strongly curved. The rudimentary lobe of the 
axis is hemispherical ; the rest of the surface is very slightly arched over the 
greater portion and concave towards the margin ; it appears to he granulated. 
The ribs are separated from one another by a narrovr shallow groove ; the 
median rib is twice the width of the three neighbouring ones and of that which 
borders the thorax, and almost three times the size of the three ribs between 
these and the first three. The limb is narrow, and has a series of rather sharp 
projections joined to one anotlier by regular curves. These points corresjiond 
to each of the ribs, but with the exception of the median projection they are 
arranged a little behind a line that would pass through the middle of the ribs. 
Dimensions . — Length of the pygidium, eleven millimetres ; breadth, 
twenty-one millimetres ; length of the rudimentary axis, three millimetres ; 
breadth, five millimetres ; width of the median lobe towards the margin, four 
millimetres; length of the projections, one to one and a half millimetres. 
