244 
AUG. F. FOERSTE 
the aperture is pear-shaped, with the narrow end on the ventral 
side. There is a tendency toward parallelism between the lateral 
walls of the hyponomic sinus, somewhat as in Gomphoceras. 
Locality and horizon . — Black River limestone on LaCloche 
Island, in northern Lake Huron. Specimen No. 1294 in the Vic- 
toria Memorial Museum, at Ottawa, Canada. 
38. MAELONOCERAS BILLINGSI SP. NOV. 
PLATE XXXIX, FIGS. 5 A, B, C 
Phragmoceras praematurum Billings, Canadian Naturalist, vol. 5, 1860, 
p. 163, fig. 19 only 
The second specimen figured by Billings under the name Phrag- 
moceras praematurum differs from the one here described as the 
type in having a shorter and straighter living chamber. It is 
assumed that the conch was much less curved lengthwise. More- 
over, the dorsal half of the aperture is more nearly circular and 
the lateral walls of the hyponomic sinus are more nearly parallel. 
Locality and horizon . — Lacloche Island, in the northern part 
of Lake Huron, in the Black River formation. Specimen No. 
1294a, in the Victoria Memorial Museum, at Ottawa, Canada. 
39. BELOITOCERAS GEN. NOV. 
Type: Oncoceras pandion Hall 
The group of conchs typified by Oncoceras pandion differs 
from typical Oncoceras in lacking a distinct gibbosity along the 
upper part of the phragmacone and the lower part of the living 
chamber. If any gibbosity along the dorsal side is present, the 
maximum development of this gibbosity is distinctly above the 
level of the base of the living chamber. Moreover, compared 
with typical Oncoceras, the conch is distinctly more flattened 
laterally. 
The relationship of the group typified by Oncoceras pandion 
is with Maelonoceras rather than with Oncoceras. Like the lat- 
ter, it is more strongly flattened laterally, and the interior of the 
living chamber is thickened below the margin of the aperture 
by an inner band which leaves a conspicuous contraction along 
casts of the interior of the conch. The aperture has an outline 
corresponding to that possessed by Maelonoceras during its 
earlier stages of growth, before the ventro-lateral saddles begin 
