10 
The second measurement is from near the point of umbilical enlarge- 
ment, and is approximate, the first is from near the anterior end of the 
ultimate whorl. The specimen is incomplete on the posterior part of the 
ultimate whorl and obscure on the inner part of the umbilicus. The whorl 
proportions are similar to those of Yakounoceras abruptum , but the size is 
much less. As little of the umbilicus is known, no comparison can be 
made of the rate of umbilical expansion. There are about 29 primary 
ribs on the ultimate whorl, less than in Yr. abruptum , and 115 to 120 (esti- 
mated) secondary ribs. The saddles are not relatively so deep nor the 
lobes so long as those of Yr, abruptum. 
The species name is given for the explorer Ingraham. 
Horizon and Locality. Collected at Alliford bay by G. M. Dawson 
in 1878, presumably from the sandstone bed near the top of the Yakoun 
formation. 
Type. National Museum of Canada, Ottawa; holotype, Cat. No. 
5012b. 
Yakounoceras torrensi n. sp. 
Plate VIII, figures 3, 4 
Diameter. 
47-0 
40-6 
27-7 
24-7 
Height, whorl 
40-4 
41-8 
39-7 
38-8 
Thickness, whorl 
56-3 
54-7 
Width, umbilicus 
33-0 
33-2 
36- 1 
37-6 
The first measurement is taken at the anterior and the last at about 
the posterior end of the ultimate whorl. The cone shape is that of a stout, 
thick-whorled serpenticone, latumbilicate to sublatumbilicate, the umbilicus 
contracting with growth. The whorl suture is on the outer edge of the 
lateral tubercles. The whorls are much thicker than high; the sides are 
narrow, somewhat flattened and divergent inside the tubercles, and wide, 
moderately convex, and convergent outside the tubercles; the venter is 
tabulate on the posterior part of the ultimate whorl (preserved) and 
rounded on the anterior part. There is about one-fourth whorl of living 
chamber preserved. The primary ribs are short and a little inclined. 
They increase in number with growth and each ends in a tubercle from 
which there proceed three narrow secondary ribs, inclined a little on the 
sides, but straight across the venter; there are also a few, single, inter- 
calated secondary ribs. The ribs are thickened and raised at the borders 
of the tabulate venter, but these modifications are lost on the anterior 
part of the last whorl preserved. There are 88 secondary ribs on the 
ultimate whorl. 
EL is long and narrow. ES is very deep and a little wider than EL 
and has a short accessory lobe on its inner side. LI is as long as EL, is 
narrow and has a long median lobule. SI is deep and narrow, but not so 
deep as ES. L2, shorter than LI, is very narrow with a long terminal 
lobule. The tubercle is on the inner border of SI. 
This is probably not a full grown specimen. The shape of ES with 
its accessory lobule, and of LI and the equal lengths of EL and LI recall 
Yakounoceras. L2, however, is much narrower than that of any of the 
known species of Yakounoceras or Seymourites. The deep ES and long, 
narrow Ll are as in Yakounoceras abruptum, but the inner whorls of that 
