23 
The whorl suture begins to advance outside the line of lateral tubercles 
at about the beginning of the living chamber. Whorl section thicker than 
high; the proportional thickness decreases rapidly on ultimate whorl, 
but the proportional height remains about the same. On ultimate whorl 
the sides are rounded and the venter arched. The living chamber is 
about eleven-sixteenths of the ultimate whorl; the last septum is at a 
diameter of 35 mm. The primary ribs increase with growth, 15 to 19 
per whorl; the secondary ribs decrease on the ultimate whorl. On the 
anterior part of the penultimate whorl three secondary ribs arise by 
trifurcation of each primary rib and, in addition, there is one intercalated 
secondary per each primary rib. In the posterior part of the ultimate 
whorl there are three secondary ribs per each primary, arising by trifurca- 
tion or by bifurcation and intercalation. This is followed by a stage 
in which there are two secondaries by furcation plus one intercalated rib, 
which passes into a stage, near the aperture of the shell, of two secondaries, 
arising by bifurcation, to each primary. The ribs are inclined very 
slightly forward on the sides; on the posterior part of the outer whorl 
they are straight across the venter, but on the anterior part are bowed 
forward; this, however, appears to have been caused by distortion or 
abnormal growth, for the curves are not symmetrical. The ribs have 
considerable relief, are narrow and fairly sharp, except on the anterior 
part of the ultimate whorl where they are somewhat broader and more 
rounded. 
The suture line is fairly simple. The ES is deeper than wide, is 
nearly twice as wide as EL, and is unequally divided by a short lobule 
into two branches, the inner one of which is the smaller. LI is about as long 
as EL, is tripartite, and is lightly asymmetric; the median lobule is fairly 
long and narrow, and almost in a median position. SI is smaller than ES, 
but is similarly unequally divided, the inner branch being the smaller. 
L2 is small. S2 is smaller than SI and about equally divided by a small 
lobule. Aux.l is about as long as L2, but is narrower and is inclined at a 
high angle. Aux.2 is very small and there are two minute, poorly defined, 
auxiliary saddles. The tubercle is on the border between SI and L2. 
The name is given for C. H. Crickmay. 
Horizon and Locality . In the lower Yakoun formation at Mackenzie 
bay, on the north side of Maude island, and in a collection taken from 10 
to 22 feet above the base of the section exposed there. 
Type. National Museum of Canada, Ottawa; holotype, Cat. No. 
9016. 
Kanastephanus mackenzii n. sp. 
Plate XVI, figures 1-3 
Diameter 
51-0 
28-1 
41-3 
47-0 
24 
49 
48-0 
30*4 
42-7 
48-3 
47-0 
29-6 
44-2 
47-6 
45- 0 
29-2 
46- 4 
45-7 
41-2 
30*7 
50-0 
43-0 
320 
32-0 
57-0 
42-0 
Height, whorl 
Thickness, whorl. 
Width, umbilicus 
Primarv ribs 
Secondary ribs 
The first measurement is from near the anterior and the last from 
near the beginning of the ultimate whorl. 
