Geol.— Vol. I.] 



SMITH— GL YPHIOCERA TW^. 



121 



Plate XIV, fig. 9, shows the smallest specimen obtained 

 of the adult stage; it agrees in all essentials with those of 

 larger growth, only the ventral saddle is shorter and the 

 lateral saddles more rounded. 



Table of Stages of Growth. 



Diameter 



Height of last 

 whorl 



Height of last 

 whorl from the 

 preceding 



Width of last 

 whorl 



Involution 



Width of umbil- 

 icus 



Proto- 

 conch. 



mm. 

 0.46=1.00 



0.24=0.52 



0.17=0.36 



0.661=1.56 

 0.07=0.15 



Proto- 

 conch and 



two 

 chambers 



mm. 

 0.61=^1.00 



0.31=0.50 



0.15^=0.24 



0.66=1.08 

 0.16=0.26 



One-half 



whorl, 

 Anarcestes 



to 

 Tornoceras 



mm. 

 0.74^1.00 



0.38=0.52 



0.13=0.17 



0.77=1-04 

 0.26=0.35 



0.06^0.08 



First 



whorl, 



Tornoceras 



to 



Priono- 



ceras. 



Priono- 



eera* 



stage 



1| whorls 



mm. mm 



0.92=11.00 1.291=1.00 



0.33=0.33 0.45=0.34 



0.23^0.25 0.29=0.22 

 0.69=0.75 0.95=0.73 



O.IO:=O.IO 0.15=:0. II 



0.28=0.30 0.50=0.38 



Priono- 



ceran 



15 whorls. 



mm. 

 1.38=1.00 



0.52=0.38 



0.31=^.22 



1.02^0.73 

 0.21=0.15 



0.51=0.37 



Priono- 



ceras 



2J whorls. 



mm. 



1.64=1.00 



0.60=0 36 



0.40=0.23 



1.38=0.84 

 0.20=0.12 



0.54=0.32 



Priono- 



ceras 



2% whorls. 



mm. 

 2.25=1.00 



0.87=0.38 



0.50=0.22 



1.82=0.80 

 0.37=0.16 



0.58=0.25 



Diameter 



Height of last whorl 



Height of last whorl from the preceding. 



Width of last whorl - 



Involution 



Width of umbilicus 



Prionoceras 



to 

 Glyphioceras . 



mm. 



2.60=1.00 



1.24=0.47 

 0.76=0.29 

 2.32=0.88 

 0.48=0.18 

 0.61=0.23 



Prionoceras 



to 

 Glyphwceras. 



End of 

 neanic. 



mm. 



3.00=:1.00 



1.45=0.48 

 0.83=0.27 

 2.82^=0.94 

 0.62^0.20 

 0.66=0.22 



Glyphioceras. 

 Anephebic. 



mm._ 

 6.00=1.00 



3-5o=o-58 

 1.80=0.30 

 6.00=1 00 

 1.65=0.27 

 0.90=0.15 



Glyphioceras 



mm. 

 11.00=1.00 



5.50=0.50 



3.00^0 27 



10.00=:0.90 

 2.50=:0.22 



i.oo=o.og 



Summary of Results. 



The ontogeny of Glyphioceras is of interest not only for 

 its own sake, but also because it is the most important genus 

 of the largest family of ammonoids of the Carboniferous, 

 and because this family gave rise to a large part of the am- 



