436 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
laminated outer part of the exoskeleton of the trumpet. Moreover, 
the epidermis which underlies and produces the exoskeleton continues 
inward to cover over the entire trumpet. Comparing this figure with 
text-figure C we may regard the trumpet as made by an inpushing of 
epidermis that has formed a very thick exoskeleton mass in its cavity. 
And this exsokeleton presents a deep narrow curved ditch enlarged at 
the bottom but with sides almost against one another and a very narrow 
opening to the surface. In all paraffin sections, even in those of an 
unused annulus from a female that had just cast its exoskeleton, the 
opening of the curved trumpet cavity to the exterior is an evident 
slit as in figure 11 (pi. 44); but a more natural condition is represented 
in very thick, free-hand sections of material cleared in oil of cloves 
as in figure 14 (pi. 44). This is a view from the left of a very thick 
section of a translucent annulus showing on the right the projecting 
tuberosity and on the left the posterior promontory, with their cavi¬ 
ties not filled by connective tissue as they were in life. The large 
central mass is the trumpet projecting dorsally from the center of 
the annulus, the ventral side being above in this view. To the right, 
in the trumpet, is seen the vestibule in optical section, passing toward 
the observer and then sweeping away toward the left. Within this 
cavity is a composite mass of wax-like material. A narrow curved 
slit passes from the vestibule toward the left to end at the outer sur¬ 
face. A like curved slit passes from the surface to the elliptical cav¬ 
ity which is the bent trumpet cavity cut across nearly at right angles. 
Focussing proved that the two slits shown, were but parts of one con¬ 
tinuous curved slit. Far to the left is the terminal recess full of sperms, 
indicated by dots. Some other sperms scattering out from the recess 
indicate a slit lying nearly in the plane of the section and leading from 
the posterior part of the trumpet and from the recess to the surface 
(compare fig. 11, pi. 44). 
The lines along which the curved slits come to the surface are the 
successive parts of the zigzag suture seen on the surface in figures I 
and 5 (pi. 43), but this is readily demonstrable only from focussing 
such a preparation as that shown in figure 5. It is there seen that the 
zigzag suture is made up of three successive lines. The anterior 
one, formed where the edges of the orifice meet, passes to the right 
and posteriorly and runs beyond the second line which in turn slightly 
runs beyond the third line that ends the suture on the median plane. 
Focussing shows a curved slit passing from the first line forward and 
