REPOET ON THE ANNELIDA. 
417 
The anterior liooks (PI. XXV a. fig. 23) have about eight teeth, the largest occupying 
the middle, the first and especially the last (which seems to be partly adnate) lieing 
smaller. The posterior hooks are less, and have a more decided dorsal curve than the 
anterior ; otherwise they are similar, having from seven to eight teeth. 
The branchiae are incomplete, but appear to number twenty-three or twenty-four. 
The absence of many posteriorly may have been accidental, but if otherwise, they are 
not continued so far backward as in Sabellaria spinulosa. 
The contents of the alimentary canal consisted of sandy mud in which were fragments 
of minute Crustacea, a few Foraminifera, fragments of sponge-spicules, minute Algse, and 
parasitic Nematoids. The latter had bluntly pointed heads and rounded tails. A few 
Gregarinse were also present. In the posterior region of the canal peculiar areolar 
membranes exist, but their relationships are doubtful. 
The complexity of the anterior region of the body in section is considerable. 
Externally it is covered by a very thin layer of cuticle, and a narrow stripe of hypoderm 
containing the pigment. The circular muscular coat is best marked dorsally, for 
ventrally, in a line with the roots of the dorsal hooks, it is merged into the intricate 
muscular mass occupying the entire area of the region. The general appearance of the 
centre of this region is somewhat like the tongue. Dorsally are the roots of the two 
great hooks, while, laterally, are the palese. The inner row has its concavity directed 
outward and backward, the dorsal end having palese circular on section, the ventral and 
outer flattened palese. Each of the latter organs has an outer chitinous investment and 
a brownish central region. The branchial processes have a somewhat rigid chitinous 
ring, which retains its shape on section, under the ciliated hypoderm, and an inner axis 
connected with the vascular supply. Considerable nerve-trunks are noticed in the 
branchial region under the ventral hypoderm. 
The intricate muscular stroma of the cephalic region shows certain changes as the 
cerebral ganglia and the mouth appear. Thus, just in front of the ganglia, a conspicuous 
band of transverse fibres occurs in the central region. As soon as the ganglia are 
outlined, a powerful transverse muscular band occurs above and beneath them, the rest of 
the area consisting of a complex series of radiate and oblique fibres. 
Behind the ganglia the intricacy of the muscular apparatus surrounding the buccal 
region is great, and the nerve-cords have now assumed a lateral position. When the 
mouth becomes enclosed the cords form two large rounded masses in section toward the 
inner and upper border of each longitudinal ventral muscle, and the dorsal muscles are 
indicated. Just before the cords unite in the first ganglion a peculiar fan-like muscular 
arrangement is caused on each side of the gullet by the fibres connected with the great 
thoracic bristles. The nerve-cords have not yet reached the hypoderm, but are invested 
by interwoven muscular fibres inferiorly, the ventral muscles externally, and the oblique 
internally. 
(ZOOL. CHALL. EXP. PART XXXIV. — 1885.) 
LI 53 
