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existence of lateral depressions or open nepionic umbilici, and the 

 usual umbilical perforation is present, although rendered very small 

 by the closeness of the coiling. 



The first air chamber observed in two specimens is unusually 

 deep and broadens laterally by growth with extreme rapidity. I 

 have not been able to expose a complete apex so as to see the cica- 

 trix, but have seen the outline of the umbilical perforation at the 

 centre. The siphuncle is closed at the end, but not perceptibly 

 swollen into a pouch as in most Nautiloids. It is not close to the 

 dorsum in the first chamber, but the csecal end is centren as shown 

 in the section of the ananepionic substage (Fig. 24, PI. iv). 



It clings closely to the dorsal side as in the young oiinternastriata, 

 as shown in Fig. 25, which represents a truncated apical chamber and 

 the paranepionic substage of the first whorl. Holm and Schroder's 

 observations have shown that it is ellipochoanoidal or has in other 

 words short funnels and a porous wall between contiguous septa. 

 Schroder's observations apply to the full-grown shell and Holm's to 

 the young.* 



The extremely rapid expansion of the whorls ceases before the 

 first whorl is completed, but it gives to the nepionic shell, when seen 

 from the venter, the aspect so common in Ammonoids during what 

 is usually called the goniatic stage. So far as now known to me, 

 no other Nautiloid possesses this peculiarity to such a remarkable 

 degree in the nepionic stage, Fig. 39, PL vi. 



The mode of growth of the siphuncle is independent of the close 

 coiling, since it has the same history in Trocholitcs inter nastriata, 

 with a large umbilical perforation, as in true Trocholites of later 

 times, with a more minute perforation. 



The septa as in most nautiloids are much wider apart, at first 

 gradually decreasing until the end of the first whorl or thereabouts, 

 as shown in Holm's figures, when they assume the normal distance 

 and are less deeply convex. The sutures exhibit corresponding 

 differences, having large ventral saddles, deep lateral lobes and 

 probably, although these were not clearly seen, dorsal saddles in 

 these earlier stages. 



The lines of growth are much straighter in the nepionic stage 

 than subsequently. The hyponomic sinus is so broad and shallow 

 that it is hardly observable on the third quarter of the first whorl 



* Holm's observations and mine are similar and I have reproduced his figure in PI. iv 

 of this paper. 



