14 
on the anterior half of the ultimate whorl, where they are fairly stout. 
These primary ribs divide into finer secondary ribs, which are small and 
very closely spaced on the posterior part of the ultimate whorl, but are 
coarser, more widely spaced, and have fewer secondary per primary ribs 
on the anterior part of the ultimate whorl. Secondary ribs have only 
moderate relief. 
The suture line is complex. The ES and SI are of about the same 
size and are a little deeper than wide. S2 is very small. LI is about as 
wide and as long as EL, is rather narrow stemmed, much longer than wide, 
and nearly symmetrical. L2 is broad and the point of furcation is on the 
outer part of it. 
The species name is given for the Spanish explorer de Fonte. 
Horizon and Locality. From talus on ledges of the lower Yakoun at 
Richardson bay, on the south side of Maude island. 
Type. National Museum of Canada, Ottawa ; holo type, Cat. No. 9009. 
Defonticeras maudense n. sp. 
Plate XIII, figure 1; Plate XIV, figures 2, 3 
Diameter 74-0 
Height, whorl 48-3 
Thickness, whorl 70-0 
Width, umbilicus 17-9 
The specimen is much distorted, so that the above measurements are 
approximate. It has stout whorls, much thicker than high, and a highly 
arched ventral area. There is a fairly narrow sulcus back of the lip and no 
ridge or second depression posterior to this sulcus. The living chamber is 
almost three-fourths of a whorl. The umbilicus of the inner whorls is very 
small and there is abrupt umbilical enlargement on the anterior half of the 
ultimate whorl. The primary ribs of the ultimate whorl are fairly stout 
and the secondary ribs are small, of low relief, decrease in number per 
primary ribs and increase in width and spacing with the growth of the 
ultimate whorl. The suture line is complex. SI is almost as large as ES 
and like it is somewhat deeper than wide; S2 is small; LI is narrow-stemmed, 
is almost symmetrical, and is about as long as EL; L2 is wider and shorter 
than LI. 
This is the largest of the species of this genus in the Yakoun formation. 
It is larger and has a more highly arched ventral area than D. defontii 
McLearn. 
Horizon and Locality. From talus on ledges of 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. 
9010. 
Defonticeras marchandi n. sp. 
Plate XII, figures 4, 5 
Diameter 50-5 
Height, whorl 43-3 
Thickness, whorl 56-9 
Width, umbilicus .... 
The above measurements were taken about one-tenth whorl back from 
the lip. The posterior part of the ultimate whorl is not preserved and the 
