627 
Fort Cassin; Coll. U.S. N. Mus. and Am. Mus., N. Y. Fig. 28, side view of 
original (slightly changed), from Whitfield, Bad? Am. Mus., Pl. xxxii, Fig. 1. 
Fig. 29, section of gerontic living chamber at the end. Fig. 30, section of ephebic 
whorl just above free end of living chamber. These two show the presence of a 
well-developed contact zone in the ephebic stage and its complete disappearance 
on the free gerontic volution. Fig. 31, shows a section of a specimen which ex- 
hibits the umbilical perforation with a core of the matrix; this cut passed inside 
of the line drawn through Fig. 35 and represents the metanepionic above the 
core and below it the paranepionic volution, the neanic being the next section 
of a volution above the metanepionic. Figs, 32 and 33, younger ages of the 
nepionic and older ages of the paranepionic volutions. Fig. 34, section along the 
line indicated in Fig. 35. Fig. 35, drawing enlarged from Whitfield’s original 
Pl. xxxviii, Fig. 7. Umbilical perforation may be somewhat larger proportionally 
than in nature. 
Figs. 36-38. Schroederoceras casinense, Quebec Group; Loc., Fort Cassin; 
Coll. Am. Mus. N. Y. Fig. 36, side view (somewhat changed), from Whitfield, 
op. ctt., Pl. xxxii, Fig. 2. Fig. 37, section of outer whorl of same near the line 
of broken shell on the living chamber of Fig. 36. Fig. 38, shows sutures on 
the venter of same specimen. 
Figs. 39 and 40. Zrocholites canadense ; Loc., Falls of Montmorency, Bronn; 
Coll. Mus. Comp. Zoology. Fig. 39 gives section. Compare with that of 77o- 
cholitoceras Walcotti. Fig. 40 shows the centre of this; the lower volution is 
the nepionic and this shows how much wider this is than the older neanic volu- 
tion above. 
