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Fort Cassin; Coll. U. S. N. Mus. and Am. Mus., N. Y. Fig. 28, side view of 

 original (slightly changed), from Whitfield, Bull. Am. Mus., PI. xxxii, Fig. I. 

 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 

 PI. 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. a'l., PI. 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. ^8, shows sutures on 

 the venter of same specimen. 



Figs. 39 and 40. Trocholites canadense ; Loc, Falls of Montmorency, Bronn; 

 Coll. Mus. Comp. Zoology. Fig. 39 gives section. Compare with that of Tro- 

 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. 



