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JOURNAL OF MARINE ZOOLOGY AND MICROSCOPY. 



false septum, beneath this again is an axillary deposit. On the inner 

 side of the shell the septum bends down to form the septal funnel 

 which reaches the preceding septum, thus making a closed tube ; at 

 the end of the funnel there is a ring of denser shell material just 

 as in the short funnels of the recent Nautilus^ 11 ). 



Ha 2 



n ff s 



Fig 4 



F.g 5 



Fig. 1. Section through the shell of Spirilla Peronii, Lam.: a, Inner 

 fibro-granular layer, covering the septum, c, by the pro- 

 longation, g ; b, outer transparent layer ; cl, false septum ; 

 e, axillary deposit ; /, ring of dense shell material at the 

 end of the siphonal funnel ; h, deposit of transparent 

 material between the end of the siphonal funnel and 

 septum ; the letter /, is placed in the siphonal cavity, a, in 

 the air-chamber. 



Figs. 2 and 3. First half whorl of Spirilla, showing in one case the 

 oval ovicell like in Bactrites and Goniatites compressus ; in 

 the other the short spherical one as in other asellate 

 Goniatites and Orthoceras. 



Figs. 4 and 5. After Amos P. Brown. Fig. 4, protoconch of Ammonites 

 as usually figured ; Fig. 5, protoconch of B acuities com* 

 pressus, Say, showing the extension of the shell in front of 

 the first septum. 



(11). Brooks, Proc. Boston Soc. Nat. Hist., vol. xxiii, p. 380. 



