PLATE XLI 
Fig'S. 1 B. Poterioceras fusiforyne (Sowerby). Diagram, , showing 
outline of conch, course of sutures along upper part of phragniacone, and 
vertical section through lower part of specimen, B, siphuncle of same 
specimen, enlarged. From Kildare, Ireland, in the Carboniferous. Speci- 
men No. 2177, in the Museum of Comparative Zoology, at Harvard Univer- 
sity. 
Fig. 2. Charactoceras haeri (Meek and Worthen). Cross-section at 
three points across the same phragmacone, to show the change in form with 
age. Same specimen as Plate XXXIV, fig. 2. 
Fig. 3 A, B. Monocyrtoceras lentidilatatum Foerste, A, cross-sec- 
tion showing location of siphuncle. B, dorso-ventral section, showing gen- 
eral outline of siphuncle. Same specimen as Plate XXXVII, fig, 1, 
Fig. 4 A, B, C. Beloitoceras pandion (Hall). A, outline of aperture, 
B, cross-section of conch. C, dorso-ventral section through siphuncle, en- 
larged. Same specimen as Plate XXXVI, figs. 5 A, B, C. 
Figs. 5 A, B. Beloitoceras jjlebeium (Hall). A, outline of aperture. 
B, cross-section of conch, at largest diameter. Same specimen as Plate 
XXXVI, figs. 4 A, B, C. 
Figs. 6 A, B. Beloitoceras lycum (Hall). A, cross-section of conch at 
largest diameter. B, dorso-ventral section through siphuncle. Same speci- 
men as Plate XXXVI, figs. 2 A, B. 
Fig. 7. Maelonoceras praematurum (Billings). Vertical dorso-ventral 
section, showing fusiform segments of siphuncle. Same specimen as pi. 
XXXIX, figs. 6 A, B. C. 
Fig. 8. Clarkoceras merciirkis (Billings). Vertical dorso-ventral sec- 
tion, with siphuncle on left side, showing concave vertical outline of seg- 
ments of the siphuncle; enlarged. Diagrammatic drawing prepared from 
the type specimen No. 826, in the Victoria Memorial Museum, at Ottawa, 
Canada. Originally described under Cyrtocerina. 
Fig. 9. Cyrtocerina typica Billings. Vertical dorso-ventral section, 
with siphuncle on left side, showing convex vertical outline of segments of 
the siphuncle; enlarged. Diagrammatic drawing prepared from the type 
specimen, No. 1301, found at Pauquette Rapids, on Allumette Island, in 
the Black River formation. In Victoria Memorial Museum, at Ottawa, 
Canada. 
