17 
(a) is taken about one-fourth whorl back from the aperture, (6) about 
one-half whorl back, and (c) at about the beginning of the ultimate whorl. 
This species has moderately stout whorls which are rounded and convergent 
on the sides and arched on the venter. The sulcus behind the lip is wide 
and behind this is a low ridge, and behind it a broad, very shallow depres- 
sion. There is nearly three-fourths of a whorl of living chamber. The 
umbilicus of the inner whorls is very small. On the last half of the ultimate 
whorl there is marked and abrupt umbilical enlargement. On the posterior 
part of the ultimate whorl there are 19 rather closely set, slightly inclined 
primary ribs of considerable relief; each divides into 2 closely approximated, 
rather stout secondary ribs; there are in addition some intercalated second- 
ary ribs; there are about 5 secondary ribs per 10 mm. in this part of the 
ultimate whorl. On the anterior part of the ultimate whorl the primary 
ribs are wider, more rounded, of proportionately less relief, and are more 
widely spaced, being about 5-5 mm. apart or spaced less than 2 per 10 mm.; 
they are, moreover, inclined a little and divide into 2 secondary ribs of 
smaller size and of low relief; there are in addition some intercalated ribs 
in this anterior part; the secondary ribs are spaced about 3 per 10 mm. 
The suture line is not complex and the saddles are relatively shallow. 
ES is deeper than SI, which is about as wide as deep; LI is wide stemmed 
and L2 is wider and shorter than LI. 
This species differs from all the above in its simpler suture line, its 
shallower saddles, and its different ribbing. It may belong to a different 
stock and is only provisionally placed in the genus Defonticeras. Stephan- 
oceras sutynicrostoma Gottsche 1 resembles this species somewhat, but 
has fewer and more widely spaced primary ribs on the posterior part 
of the ultimate whorl, and narrower primary ribs of greater relief on the 
anterior part of the ultimate whorl; the mouth border also is different. 
The sulcus behind the lip is narrower than in D. oblatum and there is no 
ridge and shallow depression behind it; the umbilical enlargement also is 
more regular. 
Horizon and Locality. Probably from the lower part of the Yakoun 
formation at Richardson bay, south side of Maude island. Collected by 
J. Richardson in 1872 and labelled “Skidegate channel”. 
Type. National Museum of Canada, Ottawa; holotype, Cat. No. 
4964. 
Defonticeras ? sp. 
Plate XI, figure 3 
The specimen so designated consists of part of an inner whorl, probably 
the penultimate whorl. The umbilicus is very small and the ribbing is as 
in Defonticeras. The suture line, however, has much deeper saddles than 
those of typical Defonticeras. With it, but not attached, is a fragment 
of an ultimate whorl, the ribbing and mouth border of which are similar 
to that of Defonticeras . 
Other specimens collected from the lower Yakoun at Richardson bay 
are too fragmental or too badly crushed for description and illustration. 
1 Gottsche, C.: Beitr. Geol, Pal. Argent. Rep. II, Pal. Theil, p. 15, PI. 3, figs. 2a, b. Cassel (1878). 
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