PLATE XXXII. 



Zone of Aegoceras Henleyi. 



Fig. 1. Aegoceras latecosta, Sowerby. 



brevispina — 



5. 



6. 



7. 



BlRCHII 



Lateral view, natural size, from the original 

 type specimen in the Sowerbian collec- 

 tion. British museum. This fossil is 

 the middle-aged condition of Aegoceras 

 Henleyi before the transformation takes 

 place (see PL XXXIII). 



Lateral view, natural size. Original type. 

 Sowerbian collection, British Museum. 



Siphonal area of the same, showing the 

 ventral row of short spines. 



Accurate tracing of the lobe-line. 



Small shell, showing details. My collec- 

 tion. 



Front view, showing spines in profile. 



Accurate tracing of the lobe-line, showing 

 the smallness of the siphonal lobe and the 

 magnitude of the principal lateral lobes. 



Young forms of this species. The series is 

 intended to show, in connection with 

 PI. XXIII, that Aegoceras Birchii main- 

 tained its original form and structure 

 through the various phases of its life. 



