33^ NEW YORK STATE MUSEUM 



i 



(visceral cone). From this last formed endosiphocone a broad/"^ 

 flattened tube with conchiolinous walls extends backward, for 

 which the term '' endosiphocoleon " is here proposed. This- 

 forms within the endosiphocone preparatory to a further with- 

 drawal of the animal and the formation of a new endosipho- 

 sheath. In apicad direction it changes into a blade, consisting 

 of two lamellae, disappearing gradually by being altered into 

 organic calcium carbonate and becoming confluent with the cal- 

 cium carbonate filling of the siphuncle. The endosiphocoleon 

 grew hence at its anterior end and was absorbed at its posterior 

 end or vanished there by secondary alteration into lime 

 carbonate. 1 



4 In the same measure as the endosiphocoleon disappears, a 

 capillary conchiolinous tube, the endosiphotube, becomes promi- 

 nent. This forms within the endosiphocoleon by the posterior 

 contraction of the siphon. It extends to the apical end of the 

 nepionic bulb, where it empties (into the protoconch which is not 

 preserved): 



5 The endosiphocoleon is flanked on both sides by conchiolin- 

 ous wings, having a crescentic section. These form on the out- :| 

 side of the angles of the flattening endosiphosheaths and are | 

 hence separated from the endosiphocoleon by the organic lime | 

 carbonate composing the endosiphosheaths. 



6 The posterior portion of the empty, ephebic siphuncle is lined 

 by the endosipholining, the anterior portion only by the septal necks 

 or funnels. 



7 The endosiphocone, endosiphocoleon and endosiphotube are 

 held in position by (mostly three) radiating suspensory mem- 

 branes (endosiphoblades), which aflix the endosiphosheath etc. 

 to the preceding endosiphosheath and the ectosiphuncle. 



8 The presence of a preseptal cone or nepionic bulb in an early, 

 otherwise typical, Cameroceras (C. brainerdi) , — while in 

 the later species of Cameroceras the nepionic bulb has disappeared — , 

 as well as in a typical Vaginoceras (V. belemnitiforme), 

 in Nanno aulema and in a Piloceras (P. explanator), 

 demonstrates that these genera have passed through the same early 



