3i6 



NEW YORK STATE MUSEUM 



Holm subsequently [1895, 17:616; 1896, 18:406] added observa- 

 tions on V. b e 1 e mn i t i f o r m e without, however, recurring 

 to his description of the endosiphuncular structure of the Esth- 

 onian material of Endoceras gladius. He states, how- 

 ever, that the latter showed that 

 structure '' remarkably well devel- 

 oped and preserved " [/. c, p.617] 

 and that also in Swedish speci- 

 mens of V . b e 1 e m n i t i f o r m e 

 (= gladius) the endosipho- 

 blade could be observed. 



The distinction apparent in our 

 material between the narrow endo- 

 siphotube and the wider endosi- 

 phocoleon, which in apicad direc- 

 tion becomes a compressed blade, 

 has not been noticed in the Euro- 

 pean material and consequently 

 Holm's term " endosiphoblade "" 

 comprised both the apical blade- 

 like continuation of the endo- 

 siphocoleon and the thinner mem- 

 branes which connect this and 

 the ectosiphuncle. 



5 Growth stages of shell 



The description of the trans- 

 verse and longitudinal sections 

 through the endosiphuncular 

 structures in their various stages 

 of development enables us now to 

 portray the processes which took 

 place within the siphuncle of Cameroceras brainerdi 

 during the animal's advance from the apical cone to the living 

 chamber at maturity. 



Fig. 16-18 Diagrammatic sections of 

 early growth stages of shell of Camero- 

 cera s braine r di 



