1915] PALAEOZOIC FossILs FROM HupsoNn Bay. 73 
ORTHOCERAS, sp. indet. 
Several fragments of an orthoceracone indicating a diameter of from 
30 to 40 mm. Septa about 6 mm. apart. Siphuncle only faintly indi- 
cated; sub-central in position. 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 334 S. Royal Ontario Museum of Palaeontology. 
ORTHOCERAS, sp. indet. 
Plate V, Figure 12. 
One fragment of a small orthoceracone or cyrtoceracone. The 
chamber of habitation is 26 mm. long; it is apparently round with a 
diameter of 15 mm. There is evidence of a very slight curvature and a 
slight contraction towards the aperture. The septa are strongly curved 
and about 2 mm. apart. The sutures are not discernible but a central 
siphuncle seems to have been present. The form is possibly identical 
with Orthoceras ommanneyi, Salter. (See ‘‘Sutherland’s Journal, etc.’’) 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 335 S. Royal Ontario Museum of Palaeontology. 
ACTINOCERAS HEARSTI, Parks. 
Plate VI, Figure 5. 
ACTINOCERAS HEARSTI, Parks. Bur. Mines of Ont., 22nd Rep., pt. I, p. 195, 1913. 
This species is founded on one well preserved specimen showing 
the siphuncle, portions of eight camere, and part of the outer shell. 
The shell is apparently round and very gently tapering, having in 
the specimen a diameter of 112 mm. The septa average 11.5 mm. 
apart; on the siphonal side of the siphuncle they are bent sharply orad 
but on the anti-siphonal side their curvature is more gentle. 
The siphuncle shows a maximum width of 50 mm.; it is strongly 
nummuloid with the rings inclined at a slight angle to the axis. On 
the internal side the rings are evenly rounded, while on the external 
side they have an orad aspect in conformity with the highly curved 
septa. The siphuncle is marginal in position lying within 3 mm. of the 
shell at the posterior end and 6 mm. at the anterior end of the specimen. 
The endosiphuncle is narrow, apparently about 6 mm. wide; it is 
somewhat excentric being placed nearer to the internal side of the 
siphuncle. The radiating tubuli seem to have been carried on infundi- 
buliform membranes as in Huronza inflecta (page 75); but in the present 
species these structures do not arise at so low an angle from the endo- 
