3IO NEW YORK STATE MUSEUM 



of the dumb-bell. This dumb-bell-like outline is again obliterated 

 in the next section, figure 7 (7.5 mm distant from 6). In this the 

 endosiphotube has again decreased since the last section to about 

 one half of its former diameter, while the endosiphocoleon has 

 retained its width. In the next it has even again become broader. 

 Its ends are notably rounder and thicker than the middle of the 

 plate and a fine central line can again be traced, indicating the 

 composition of the blade of two conjoined lamellae. The entire 

 endosiphocoleon, which before had swung to one side, has re- 

 turned again to the median line of the siphuncle. 



In this condition the endosiphocoleon remains to the apical end 

 of this (not complete) siphuncle, i. e. it extends across the siphuncle 

 as a dark gray brown band with indistinct outline which includes 

 the fine endosiphotube; its swollen lateral extremities touching or 

 coalescing with the gray wall of the siphuncle. Figure 10 is taken 

 15 mm from the preceding section and shows no material change 

 from the latter. It shows white cross-lines which transect the brown 

 band of the endosiphocoleon. These are due to secondary crystal- 

 lization, the endosiphocoleon being — in contrast to the irregular 

 crystallization of the remainder of the interior of the siphuncle — 

 composed of two layers of parallel crystals which distinctly grew 

 from the median line of the endosiphocoleon as a base. 



Text figure 1 1 shows the position and extension of the endosipho- 

 coleon in a very early portion of the siphuncle or near the apex 

 [see fig. 7]. It is here a light brown transverse band with a 

 central black conchiolinous endosiphotube. This condition is 

 reached shortly behind the endosiphocone in the earlier portions 

 of the siphuncle, when its diameter is still small as is exemplified 

 by the section [pl.8, fig.i]. 



In order to obtain a complete portrayal of the endosiphocoleon 

 and endosiphocone of Cameroceras brainerdi we 

 will add the description of a few other sections which show 

 features slightly dififerent from or explanatory of those observed 

 in the series of sections noted above. There is, first, the longi- 

 tudinal section [pl.9, fig.2] in vv^hich a well preserved endosiphocone 

 with sheath is exhibited which at its apex contains a newly 



