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the whorl finally into contact is more gradual, so that the umbilical 

 perforation is larger and the contact occurs in the usual way on the 

 ventral side of the ananepionic substage, instead of on the dorsal 

 side of the metanepionic substage, as in Trocholites. 



The whorl has short ventro-dorsal and longer transverse diameters, 

 or broad whorls like many species of Trocholites, but is like a broad 

 whorled typical, nautilian form from the earliest stage and has not 

 the kidney-shaped outline so common in sections, especially of the 

 younger stages of the shell in Trocholites. 



The modifications of this outline through the flattening of the 

 abdomen and lessening of the gibbosity of the sides occurs doubtless 

 at different stages in different species, but in Schroederoceras angu- 

 latum and Saemanni it is fully developed only in adults. 



The contact furrow is well marked in the young and continues in 

 some species to be a well-defined depression throughout life, becom- 

 ing, however, somewhat less marked in the free part of the whorl or 

 gerontic stage. In some species it is very faintly marked ap- 

 parently before this stage is reached. It seems to be dependent 

 upon the closeness of the coiling and involution, which is as a rule 

 very slight at all stages in the ontogeny and all stages in the 

 phylogeny. It is consequently somewhat remarkable that this zone 

 should persist upon the dorsum of the shell so long after the whorl 

 becomes free of pressure on that side in the gerontic stage. 



The siphuncle does not apparently, so far as is seen, materially 

 change the position it has at the end of the first whorl. It may, as 

 in Saemanni, become slightly more removed from the dorsum, but 

 in angulatum it is very close to the dorsum, even in the ephebic 

 stage. The walls of this organ are thick, and it is often preserved 

 in the middle of loosely crystalline calcareous deposits under condi- 

 tions which are not usually considered favorable for the preserva- 

 tion of siphuncles. 



Schroederoceras angulatum. 



Lituites angulatum Saem. (Palentogr., iii, PL xxi, Fig. \a-b ; not 

 c-d). 



Loc, Brevig, Norway. 



The original of the Lit. angulatus of Saemann (Fig. ia-b) is in the 

 Mus. of Comp. Zoology. It has a subquadragonal whorl in the 

 ephebic stage with a flattened and slightly concave abdomen. The 

 shape in cross section is peculiar and quite different from that in 

 Fig. id. The abdomen on the living chamber is slightly elevated 



