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great rapidity upon the venter in order to swing that part around 

 the very sharp curve made by the gyroceran bend. 



The paranepionic substage has well-marked longitudinal ridges 

 and transverse bands of growth given in Fig. 6. The latter part 

 of the paranepionic in this species, if this be properly limited by 

 means of the ornamentation, is close coiled. That is to say, it 

 touches dorsum of the ananepionic and envelops it, the involution 

 being almost complete from the very beginning. 



The umbilical perforation is, however, not completely closed nor 

 is it subsequently closed by extra growths of shell as in Nautilus 

 pompilius. The area of the umbilical zones is marked off at an 

 early age by the smoothness of the shell, the longitudinal ridges 

 being absent on these parts. In some specimens the shell mark- 

 ings are much stronger than in others, but in all they seem to grow 

 more decided until near the end of the metaneanic substage. 



The meta- and paranepionic substages have an elevated subangu- 

 lar abdomen not shown in any of the figures, the outline of the 

 section of the whorl is in reality in these early substages depressed 

 subtrigonal similar to the young whorl of Cymatoceras, but less 

 acute, and to that of Nautilus pompilius, but more pronounced than 

 in that species on account of the subangularity of the venter; the 

 venter of Nautilus pompilius being more rounded in the paranepi- 

 raiic substage. 



The ananeanic and metaneanic are blended and probably not 

 separable, but the paraneanic can be distinguished. The former 

 has the siphuncle tending more towards the centre, although in 

 some specimens this alteration is not so great as in others. The 

 transverse bands become broader and their edges have tubercular- 

 like short ridges on a secondary band, which are sometimes well 

 marked off on their apical borders from the sunken younger parts 

 of the same bands of growth. These ridges are always continuous 

 from band to band and over the sunken parts of each band. In 

 the paraneanic substage, as shown in Figs. 7 and 8, these ornaments 

 begin to diminish and finally die out. In Fig. 8 this substage is 

 limited by the retention on one side of a partial constriction or 

 permanent aperture, which, however, is not present in all shells. 



In the anephebic stage, also shown in Figs. 7 and 8, orad of the 

 constriction, the shell is very nearly as smooth as it is in the full 

 grown. The form of the whorl remains about the same. The 

 siphuncle has become dorso-centren in position in this shell, in 



