298 NEW YORK STATE MUSEUM 



several specimens. In the opposite or apical direction it extends close 

 to the tip of the siphuncle. This internal lining layer of the siphuncle 

 will be termed in this paper " endosipholining " [see p.303]. 



The third part of the siphuncle is that which has been filled 

 by the endocones, but is still surrounded by the cameras of the 

 phragmocone. The endocones have mostly become obliterated 

 by the formation of coarse white calcite, but from the endosi- 

 phuncular canal there still proceed at intervals short lines which 

 are parallel to the last endocone and represent the bases of 

 former endocones {see pl.Q, fig.2]. Occasionally also the entire 

 walls appear still as gray lines in the calcite filling [see pl.6, fig.3]. 

 The " dart " or " Spiess " extends at its apical end into a flat broad 

 tube, which frequently passes through nearly the whole width of the 

 siphuncle and which possesses strong, deep black walls of velvety 

 appearance, suggesting their composition of conchiolin. This flat 

 tube is the first part of the endosiphuncle.^ The latter passes through 

 the whole length of the siphuncle. Its characters are such as to 

 invite detailed description, which will be given below. 



The fourth part of the siphuncle of this species is that which 

 projects apicad beyond the camerated portion of the shell (the 

 phragmocone), and which, hence, was entirely free. This part 

 is identical with the apical cone of Nan no aulema Clarke 

 and Vaginoceras belemnitiforme Holm. It is, 

 however, not short and strongly inflated, but long and gradually 

 widening at approximately the same rate as the anterior parts 

 of the siphuncle. This free portion may have easily reached 

 a length of 70 mm as the finely preserved specimen reproduced 

 in plate 6, figure 3 indicates. 



It might be presumed that in the specimens in hand the septa 

 continued further apicad than their present preservation would 

 indicate, and that the free apical cone is more due to incomplete 



iWe use here provisionally, till further definitions have been given, Hyatt's 

 term " endosiphuncle " for the central tube of the siphuncle. Hyatt's defini- 

 tion is [1900, p.515] : "Organic deposits in the form of endocones, and taper 

 off at the center into a spire that is sometimes tubular and .hollow, or again 

 flattened and elliptical. This is the endosiphuncle." Before this definition 

 the term " endosiphon " had been in use for the same organ. 



