32 
Coelenterata I liave already described, is the only fact that makes me think 
that it is of the same age as these, and that it represents Upper Silurian 
deposits. The specimen was found on the banks of the Murrumbidgee, near 
Yass. 
EUOMPHALUS, Sowerhy. 
Sub-genus— 0 IIP SAL 0 TB 0 CSUS, Meek. 
Euomphalus (Omphalotrochus) Claekei, L.G. de Koninck. 
PI. I, fig. 7. 
Shell trochiform, imperforate, composed of five or six spiral whorls 
enveloping one another for about half their length, base depressed, slightly 
concave in the middle ; the last whorl is greatly developed, and comprises 
more than three-quarters of the entire length of the shell ; the lower margin 
is angulated ; the portion between the edge and the suture is slightly convex ; 
the spire is very short and the apex obtuse ; the test is very thick. The 
surface, as well as having several varices of irregular shape and distribution, 
is ornamented by a large number of lamellae, imbricating from before back- 
wards, of which the edge parallel to that of the peristome has a sigmoidal 
shape on the dorsal portion of the last whorl and curves towards the base, 
or all converge towards the end of the columella ; in any case, at a short distance 
from the angle that bounds the base the lamellae form a slight puckering 
along a very narrow band, and so form a faintly-marked concentric keel which 
proves the presence of a canal or posterior siphon. This condition, together 
with the sigmoidal outline’ of the lip, reminds one very much of the apertures 
of Suomphcdus discors and rugosus, Sowerhy, from the Silurian of Dudley, so 
that, in spite of the want of an umbilicus, their resemblance does not strike 
one at once, and is not easy to see that all belong to the same group. 
According to Bayan, of the Ecole des Mines, Paris, who, a short time before 
his death, gave me some information on this subject, this group, in which he 
also placed some other species, could be placed under the genus Omplmlotro- 
chus, proposed by Mr. Meek for an analogous Carboniferous species from 
California.* Although the peristome is angular, the transverse section of the 
whorls proves that the mouth is in reality circular ; the internal or columellar 
border is covered by a thin somewhat extended callosity. I kaow no species 
that can be compared to this one. 
* Geological Survey of California, Palasontology, i, p. 15. 
