16 
whorls appears to be larger, the primary ribs appear to be fewer and some- 
what stouter, and it has more secondary ribs per each primary. 
The species name is given for Captain Colnett. 
Horizon and Locality. In the lower part of the Yakoun formation at 
Richardson bay, south side of Maude island. 
Type. National Museum of Canada, Ottawa; holotype, Cat. No. 
9012. 
Defonticeras ellsi n. sp. 
Plate XIII, figures 2, 3; Plate XIV, figure 1 
Diameter 
61-7 
52-1 
42-8 
Height, whorl 
38-91 
45-8 
51-0 
Thickness, whorl 
57 -0 1 
60 -5 l 
70 -0 1 
Width, umbilicus 
23-1 
13-8 
9-5 
One side of the specimen is crushed, the other side is well preserved, 
but only the inner part of the apertural margin is complete. This species 
has moderately stout whorls with somewhat flattened sides and well- 
arched venter. Because of the difficulty of preparing the suture line, the 
length of the living chamber is not known; it is a whorl or less. Judging 
from the remnant of the apertural margin, the sulcus behind the lip is 
very narrow. The umbilicus of the inner whorls is very small. There is 
fairly abrupt umbilical enlargement on the last half of the ultimate whorl. 
Primary ribs are broad, particularly so on the last half of the ultimate 
whorl, have considerable relief, and are a little inclined. The secondary 
ribs are smaller, are of fair relief, and are straight across the venter. The 
suture line is complex; SI is a little smaller than ES; both are deeper than 
wide; L2 is fairly wide and the furcation of the ribs takes place about on the 
border between SI and L2. 
D. defontii has thicker and somewhat higher whorls, somewhat flatter 
sides, wider and less arched venter, and saddles not so relatively deep. 
D. maudense is much larger, and has much stouter whorls. D. marchandi is 
smaller and has relatively shallower saddles and shorter lobes. D. colnetti 
has a less proportional decrease in thickness and height on the ultimate whorl, 
a more broadly arched ventral area, and a somewhat less delicate suture line. 
The name is given for R. W. Ells. 
Horizon a?id Locality. In the lower part of the Yakoun formation 
at Richardson bay, on the south side of Maude island. 
Type. National Museum of Canada, Ottawa; holotype, Cat. No. 
9013. 
Defonticeras oblatum (Whiteaves) 
Plate XV, figure 1 
1876. Ammonites loganianus Whiteaves, Form A, Geol. Surv., Canada, 
Mes. Foss., I, pt. 1, p. 29, PI. 4, figs. 2, 2a. 
1884. Stephanoceras oblatum Whiteaves, Geol. Surv., Canada, Mes. Foss., 
I, pt. 3, p. 209. 
(a) 
(b) 
(c) 
Diameter 
58-0 
49-0 
37*5 
Height, whorl 
37-5 
43-8 
53-8 
Thickness, whorl. 
55-5 
62*8 
74*5 
Width, umbilicus 
25-0 
15*7 
1 Approximate. 
