462 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
In some specimens the plateau is nearly smooth as in figure 34 (pi. 
47), in others the suture is at the bottom of a somewhat pronounced 
valley and the sides of this valley often stand up as ridges parallel to 
the suture. Anteriorly, especially, these ridges are very pronounced 
and tend to simulate the tuberosities of C. affinis though they are never 
as prominent. 
Removing the exoskeleton of the annulus and regarding its dorsal 
surface (pi. 48, fig. 36), we find it the obverse of figure 34 (pi. 47), 
that is, from its edges there is a steep slope down into a deep pit with a 
flat bottom. Across this runs, deep down, a small simple trumpet- 
ridge ending posteriorly in a bulb and anteriorly continuous with the 
deeper, ventral part of the groove of the anterior face (pi. 48, figs. 36, 
37, 38). Like almost all of the annulus, the dorsal ridge or trumpet 
is highly calcified, floating in alcoholic picrosulphuric with evolution 
of gas, and it looks like a piece of glazed china. 
The surface of the groove on the anterior face of the annulus is 
glazed and yellowish. The entire organ seems to have little flexibility 
and the introduction of sperm into it would seem to present difficulties. 
Decalcified and cleared, a ventral view of the annulus (pi. 46, fig. 
24) shows its great simplicity. Seen through the exoskeleton of the 
top of the plateau the 
trumpet ridge is a thick- 
walled tube with three 
bends, right and left alter¬ 
nately. This tube follows 
the suture very closely 
Fig. D. and its cavity is nowhere 
far removed from the su¬ 
ture. Moreover, the suture like the tube shows but a simple and con¬ 
tinuous change in course with little of the character of successive 
straight lines seen in C. affinis and C. virilis. 
The cavity of the trumpet connects bv very short clefts with the 
suture and in paraffin sections these gape open as shown in text-figure 
D which represents a cross section of the posterior part of the 
annulus. 
In nature the suture is closed except for a small chink anteriorly 
near the median line (pi. 46, fig. 24), and this represents the orifice 
and leads into a very shallow and simple vestibule or anterior part of 
the trumpet tube. The tube does not therefore open anteriorly into 
i 
