7 
As already noted, S. plenus (McLearn) is similar in ornament, but has 
stouter whorls and a somewhat smaller umbilicus. 
Horizon and Locality . Collected at Alliford bay by G. M. Dawson in 
1878, presumably from a sandstone near the top of the Yakoun formation 
at that locality. 
Type. National Museum of Canada; holotype, Cat. No. 5012. 
Seymourites multus n. sp. 
( multus , many) 
Plate III, figure 2 
Diameter 145 
Height, whorl. 37 
Thickness, whorl 42 
Width, umbilicus. 36 
The above measurements are approximate, for the specimen is dis- 
torted, particularly in the umbilicus. They have been made at the anterior 
end of the specimen, the only place where direct measurement of the 
diameter is possible. The ribs, both primary and secondary, are numerous; 
there are about 5 secondaries to each primary on the ultimate whorl, 5 
branching from the small tubercle at the end of each primary or 4 branching 
and one intercalated. The primary ribs are angular and outside the inner 
margin are a little inclined. The secondary ribs are a little inclined on the 
sides, but are straight across the venter; they also are narrow and elevated. 
Only a part of the suture line can be prepared. It is deeply cut. ES is 
only partly preserved and the total length of the accessory lobe cannot be 
obtained, although it is evidently fairly long. SI has a long accessory 
lobe and is about as deep as it is wide. Only a part of LI is preserved and 
the total length of the median lobule cannot be determined. L2 is some- 
what as in S. plenus (McLearn). The tubercle is on the inner side of SI. 
The proportions and size are much as in S. plenus, but the relative 
height of whorl is less and the umbilicus is greater. The ribs, both primary 
and secondary, are more numerous than in either S. plenus or S. loganianus 
(Whiteaves). The suture line is sufficiently like that of S. plenus to admit 
of its assignment to the same genus. 
Horizon and Locality. In a sandstone bed near the top of the Yakoun 
formation, on the northeast shore of Maude island. 
Type. National Museum of Canada, Ottawa; holotype, Cat, No. 
9001. 
Genus, Yakounoceras McLearn 
1927. Yakounoceras McLearn, Trans. Roy. Soc., Canada, 3rd ser., vol. 21, 
sec. IV, p. 71. 
This genus agrees in shape and ornament with Seymourites and the 
description of these features under Seymourites applies also to Yakounoceras. 
Although the preservation is poor, there appears to be evidence (See Yr. 
abruptum ) of less involution of the inner whorls and of some umbilical 
contraction up to the stage of growth of the anterior end of the penultimate 
whorl and the posterior part of the ultimate whorl; at any rate at this 
stage the cone shape is near sphaeroconic, and angustumbilicate to sub- 
angustumbilicate. On about the anterior half of the ultimate whorl 
there is umbilical expansion and eccentruinbilication and some whorl 
