486 
and the markings resemble those of that genus, as does also the 
development of the siphuncle. The larger size of the umbilical 
perforation is interesting, but this alone does not warrant generic 
separation. 
TROCHOLITES CANADENSIS, Pl. iv, Figs. 23 and 24, and Pl. vi, 
Figs. 39 and 4o. 
Loc., Falls of Montmorency, near Quebec. 
The four specimens representing this species came from the 
Bronn collection. They are similar to 7. ammonius 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 
cost 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 Z. ammonius or 
any other described species of Trocholites. 
The extremely broad aspect in section of the ananepionic volu- 
tion is given in Fig. 24, asseen 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 
