PLATE XXXIX 
Fig'. 1. Monocyrtoceras lentidilatatum Foerste. Dorsal view, in- 
verted in order to illuminate the side best preserved; with one segment 
of the siphuncle exposed. Same specimen as Plate XXXVII, fig. 1. 
Fig. 2A, B. Oncoceras constrictum Hall. A, lateral view; B, ventral 
view of same specimen, showing surface striae. From Middleville, New 
York, in the Trenton limestone. Same specimen as 3rd Rep. New York 
State Museum, 1850, pi. 3, figs. 3 a, b. 
Fig. 3. Oncoceras constrictum Hall. Lateral view, exposing base of liv- 
ing chamber. From Middleville, New York, in the Trenton limestone. 
Same specimen as Pal. New York, 1, 1847, pi. 41, figs. 6 a, b, c. 
Fig. 4. Oyicoceras constrictum Hall. View of septum at base of another 
specimen, showing passage of siphuncle through septum. From Middle- 
ville, New York, in Trenton limestone. Same specimen as Pal. New York, 
1, 1847, pi. 41, figs. 7 a, b, c. i 
Figs. 5 A, B, C. Maelonoceras billingsi Foerste. A, lateral view, with 
ventral side on left. B, view of aperture. C, ventral view. From LaCloche 
Island, in northern Lake Huron, in the Black River. Specimen No. 1294, 
in Victoria Memorial Museum. One of two specimens described and 
figured by Billings under Phragmoceras praematurum. 
Figs. 6 A, B, C. Maelonoceras praematurum (Billings). A, dorsal view. 
B, lateral view with ventral side on left. C, lateral view with ventral side 
on right, surface showing transverse striae. From LaCloche Island, in 
northern Lake Huron. One of two specimens described and figured under 
Phragmoceras praematurum. See also Plate XLI, fig. 7. 
