1881. 
225 
[Burgess. 
ends in a perfectly closed seam. A section through the middle of 
the head will, however, at once clear up the whole mystery, show- 
ing that the upper and lower lips are locked together by a dove- 
tail joint, the character of which is plainly shown by figures 2, 3, 
and 4, (m. 1.) This mouth-lock extends the whole width of the 
head from the base of one mandible to the other, and if we open 
and close the mandibles we see that, while the basal opening of 
the mandibular canal is exposed when the mandibles are extended 
(see the left mandible — right side of the cut — in figure 1), it is 
brought into the comer of the mouth when the mandibles are 
closed (see the right mandible in figure 1), and these being natu- 
Fig. 2. Longitudinal section through middle of head, X 18, showing the mouth- 
lock (to. I .), the mouth cavity (to.) with its thick floor, and the ridge in its roof for the 
insertion of the frontal muscle, f.m. ph., Pharynx with its muscular investments and 
its suspensory muscles, the two posterior series s. to . 1 and s. to . 2 , behind the brain, hr. 
g.p The suboesophageal ganglion, f. g., Frontal ganglion, p. to., Muscle attached to 
mouth process. Ibm., Labrum with base of labial palpus. 
rally in this position when buried in the body of a victim, the 
water-tiger sucks up the former’s blood as a man inhales the smoke 
of a pipe stuck in the side of his mouth. 
The mouth cavity is of small diameter, and somewhat crescent- 
shaped, as shown in figure 1, where the roof is exposed from 
above on the right side. The roof is formed of a flexible mem- 
brane, while the floor is heavier and rigid (see figures 2 and 4). 
Along the middle of the roof runs a hard chitinous ridge (figures 2 
and 4, r.) to which, on each side of the head, a powerful muscle 
PROCEEDINGS B. S. N. H. VOL. XXI. 15 JANUARY, 1882. 
