15 
umbilicus is obscure. It is a much smaller species than either D. defontii 
or D. maudense and has more slender whorls than either, both proportional 
height and thickness being less. The sides of the whorl are somewhat 
flattened, but the ventral area is well rounded. The sulcus behind the 
lip is fairly wide and the ridge posterior to that is broad, but has little 
relief. Behind this is a very shallow, hardly perceptible, depression. The 
primary ribs are of moderate stoutness and relief on the core, and anteriorly 
increase evenly in size and width of spacing. The secondary ribs are 
numerous, particularly on the posterior fialf of the ultimate whorl; they 
are more numerous on the anterior half of the ultimate whorl than in D. 
defontii. 
The suture line is fairly complex; ES is about as deep as broad; SI is 
similarly proportioned, but a little smaller; LI is nearly as wide as EL, and 
about as long; L2 is broader and more shallow than LI; the point of fur- 
cation of the ribs is in the outer part of L2. 
The species name is given for Captain Etienne Marchand, an early 
explorer of the islands. 
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. 
9011. 
Defonticeras colnetti n. sp. 
Plate XIII, figures 4, 5 
Diameter. ... . . . . 
Height, whorl. . . 
Thickness, whorl 
Width, umbilicus 
53-8 
49-2 
63*5 
40-0 
50*0 
68*5 
The first measurement is taken about one-eighth whorl behind the lip 
and the second at the beginning of the ultimate whorl. The specimen is 
somewhat distorted. The preservation of the umbilicus is poor, but it 
appears to be very small in the inner whorls and the umbilical expansion 
on the ultimate whorl is marked and abrupt. It is a smaller species than 
D. defontii , has thinner whorls, and the decrease in proportional thickness 
and height on the ultimate whorl is not so great. It is larger than D. 
marchandi and has stouter whorls; otherwise the whorl shape recalls that 
species, for the sides are similarly somewhat flattened, although not so 
much so, the sulcus behind the lip is not well preserved, but is apparently 
not so wide as in D. marchandi and is deeper on the sides. The ribbing is 
similar to that of D. marchandi , there being about 3 secondaries to each 
primary on the anterior part of the ultimate whorl and the increase in size 
and wudth of spacing are proportionately much the same. Of course the 
ribs are actually larger in this species, being comparable with its greater 
size. The saddles are proportionately deeper and the lobes longer than 
in D. marchandi. SI is about as large as ES; LI is as long, but not as wide 
as EL; L2 is wider than LI. The point of furcation of the ribs is on the 
border between SI and L2. 
Sphaeroceras cf. submicrostoma Gottsche, as identified by Boehm 1 , 
has a somewhat similar form and ribbing, but the umbilicus of its inner 
1 Boehm, G.: Nova Guinea, Resultats I/erp6dition scientifique Ne’er lan daise & la Nouvelle- Guin6e ea 1903, 
vol. 6, G6ologie, Abschnitt I, p. 11, PI. 2, figs. 3a-c not 4 (1912). 
64178—2 
