304 ' NEW YORK STATE MUSEUM 



the first to clearly recognize it, " schwertahnliches Blatt " [1887]. 

 Later [1895] the same author introduced the term " endosipho- 

 blade " (" endosiphobladet " in the Swedish original) and defined 

 it as the thin calcified endosiphuncular membrane which extends 

 longitudinally in several species of Endoceras and Piloceras and 

 connects the endosiphotube and endosiphocone with the inside 

 of the ectosiphuncle. It becomes evident from the discussion of 

 this organ in the last cited publication that this term is meant 

 to comprise both the hollow blade and the calcified suspensory 

 membranes. 



Since we shall show in this paper that the endosiphotube is a 

 new formation, at least in our species, within the broad hollow 

 endosiphuncular part, first called " schwertahnliches Blatt " by 

 Holm, and also that the latter and the suspending membranes 

 are of different origin in our form, it becomes desirable to dis- 

 tinguish between these two organs which are comprised in 

 Holm's term " endosiphoblade." We will therefore, in view of 

 Holm's definition, retain this latter term for the suspensory mem- 

 branes and designate the broad and originally hollow endosi- 

 phuncular " Blatt " by a new term. 



Holm named the species, in which he observed it, Endo- 

 ceras gladius in allusion to this swordlike blade. " Gla- 

 dius" would therefore be an appropriate term, were it not for the 

 fact that this word is already used for the cuttlebone or pen of 

 the cuttlefish. For this reason we shall use here instead the 

 word *' coleon," and to make it conform with the other terms, 

 call this flattened tube the " endosiphocoleon." i\s " endosipho- 

 sheaths " we designate the walls of the funnel-shaped endosipho- 

 cones (Hyatt's '' endocones "), which are left behind by the 

 advancing animal. 



3 Endosiphocoleon and endosiphotube 



As we have noted above, Holm was the first to observe, in a 

 species obtained in Esthonia from a transitional bed between the 

 Vaginatenkalk and Echinosphaeritenkalk, the organ which we have 

 found still more peculiarly developed in an American species 



