ANDREWS: ANNULUS VENTRALIS. 
437 
dorsally as well as to the right to open into the vestibule and first part 
to the trumpet tube and a second curved slit passing dorsally in a curve 
chiefly to the right, to open into the posterior part of the trumpet tube, 
while a third slit from the median line passes dorsally a slight distance 
and has complicated relations to the recess, to be described below. 
The three slits are in reality but parts of one curved slit sinuously 
bent where opening into the trumpet dorsally and sharply bent in 
lines where coming to the surface as the zigzag suture. It must also 
be borne in mind that the suture, as shown in figure 1 (pi. 43), passes 
in a vertical curve over the promontory and then slantingly downwards 
to the left. Where the successive lines of the suture meet there are 
side puckerings of the suture, and there are other minor side folds. 
Morphologically we may regard the trumpet as a sort of flat pocket 
folded from side to side and with its mouth represented anteriorly 
by a crescentic orifice and along the rest of the pocket by a nearly 
closed suture. The lining of this pocket is exoskeleton so thickened 
as to leave only a narrow, bent slit from the suture down to the rounded 
bottom of the pocket which thus becomes a partly shut off trumpet¬ 
like cavity. 
But there is a peculiar complication at the posterior end of this 
morphological pocket and that is the recess above mentioned which 
in turn may be interpreted as side pouches from the main pocket. 
Owing to the number of curved spaces and their walls seen in trans¬ 
parent material and to the fact that continuous series of thin paraf¬ 
fin sections are difficult to obtain, much time was spent in arriving 
at a clear conception of this recess in this species of Cambarus. 
The recess may be described as a lateral and posterior extension 
of the tip of the cavity of the trumpet, somewhat in the shape of a 
pair of saddle-bags. Seen from the ventral side (pi. 43, fig. 5), the 
recess appears as a rounded sac often full of sperm. When more 
magnified this mass of sperm looks somewhat heart-shaped (pi. 47, 
fig. 27). This figure shows the promontory in a transparent prep¬ 
aration of the specimen from which the section figure 14 (pi. 44) was 
subsequently cut. On the surface the posterior, middle, and part of 
the anterior lines of the zigzag suture are shown as lines bounded by 
opaque bands indicating the dipping in of the exoskeleton at the bot¬ 
tom of superficial grooves and the practically closed up state of the 
slits leading dorsally to the cavity of the trumpet. The posterior line 
of the suture passes beyond the heart-shaped mass of sperms both 
