1915] PALAEOZOIC FossILs FROM HupsoN Bay. 63 
species can be easily differentiated from a young example of E. rotundus 
by the shape of the whorl and the lack of an apical depression. 
Locality—Above Limestone rapids, Severn river, District of Patricia. 
Horizon—Silurian. 
No. 369 S. Royal Ontario Museum of Palaeontology. 
EUOMPHALOPTERUS TYRRELLI, Parks. 
Plate III, Figures 15 and 16. 
EUOMPHALOPTERUS TYRRELLI, Parks. Bur. of Mines of Ontario, 22nd Rep., pt. 1, p. 194, 
1913. 
This species is founded on a single fragmentary cast showing the 
interior of part of the body whorl and part of the alar expansion or 
carina of the first whorl of the spire. The extraordinary size of the 
specimen has induced me to attempt a restoration of the shell which 
is shown in Plate III, Figure 15. While this figure shows correctly 
the size and general shape of the shell, it is to be understood that the 
whole of the ornamentation has been restored from the markings dis- 
closed on the mould of the alar expansion of the first whorl of the spire. 
The direction of the lines of growth on the alation and on the outer 
aspect of the volutions is correct, but the direction on the upper side of 
the volution was not disclosed in the specimen, and has been restored 
without any supporting evidence. 
The cast indicates an actual width for the interior of the shell of 
200 mm.; adding to this the extent of the alation the total diameter was 
at least 295 mm. and may have been greater, as there is no evidence in 
the specimen that the whole of the body whorl is preserved. The cast 
of the first volution at its maximum point shows a width of 51 mm. 
anda height of 36mm. It is evenly rounded on the interior and rather 
flat on the upper surface to within about 20 mm. of the outer margin. 
At this point it falls off rapidly to a sharp edge almost at the base of 
the whorl. The under side shows a slight concavity within the outer 
margin and then a rather stronger convexity which fades into the evenly 
rounded interior aspect. The spire is gently ascending, as the base of 
the cast of the second volution is about on a level with the upper sur- 
face of the first volution, and is separated from it by an interval of 
18 mm. Although nothing is known of the inner whorls, this method 
of coiling would indicate only three or four whorls in all. 
A fragment about 100 mm. long shows the impression of the alation 
of the second whorl which bridges over the interval between the internal 
casts of the two whorls and reaches about half way across the upper 
flat surface of the outer whorl. The actual width of the alation at this 
