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and the markings resemble those of that genus, as does also the 

 development of the siph uncle. The larger size of the umbilical 

 perforation is interesting, but this alone does not warrant generic 

 separation. 



Trocholites Canadensis, PI. iv, Figs. 23 and 24, and PI. vi, 

 Figs. 39 and 40. 

 Loc, Falls of Montmorency, near Quebec. 



The four specimens representing this species came from the 

 Bronn collection. They are similar to T. ammonias in form, but 

 differ in being broader proportionately in the transverse diameters 

 of the whorls and have deeper umbilici. The whorls are rounded, 

 there being no tendency to angularity, either of the sides or abdo- 

 men, and in these specimens the size is small. There are fold-like 

 costae from an early neanic stage and the living chamber may be 

 considerably over one-half of a volution in length. The exterior 

 is marked by longitudinal lines along the venter and often on the 

 sides, but these have none of the regularity and prominence observ- 

 able in Conrad's figure, and that figure shows no costations which 

 are more prominent and fold-like in this than in T. ammonius or 

 any other described species of Trocholites. 



The extremely broad aspect in section of the ananepionic volu- 

 tion is given in Fig. 24, as seen from the front. The umbilical 

 perforation between this and the larger paranepionic volution is 

 very narrow. In Fig. 23 looking through the transparent para- 

 nepionic volution one sees the umbilical perforation and the meta- 

 nepionic volution as it is turning or revolving around the core 

 of the perforation. The outlines in both of these views belong to 

 different ages and are, consequently, quite distinct. The upper 

 section of a whorl in Fig. 24 is the ananepionic substage; the upper 

 section in Fig. 23 is a visual section of the metanepionic whorl just 

 before it changes by growth into the paranepionic, which is seen 

 below in same figure, and this last in turn is younger than the 

 lower section in Fig. 24, which is a later age of the same substage. 

 Taking these in regular order, it is seen that the ananepionic has a 

 rounded dorsum and almost digonal whorl on account of its very 

 rapid transverse growth ; that this, as it becomes older, acquires a 

 concave dorsum in the metanepionic of Fig. 23. Then, as the 

 whole revolves while growing, at a later age but part of this same 

 substage, after the shell has passed this bend and is freer to grow on 



