NERINIDES TRIDENTATA. 48] 
Branchiz arise on the second bristled segment ; dorsal lamella as long as the branchia to 
which it is attached. No dorsal hooks. Anal sucker. 
Mesnil and Caullery! (1917) describe this species as dimorphic, some eggs develop ng 
to typical Spionid larvee, whilst others in the spawn-mass develop directly without a pelagic 
stage. Moreover, in the latter case cannibalism occurs, the authors assigning the title 
adelphophagy to the condition (the peecilogony of Giard). De St. Joseph met with Trichodina 
pediculus as a parasite on the branchiz ; whilst in the interior of the branchiz and the 
tentacles he found encysted Distomes, which might have been introduced by the Rissoz. 
NERINIDES TRIDENTATA, Southern, 1914. Plate CX XXIII, fie. 19—hook; Plate CXX XVI, 
fig. 7—tenth foot. 
Specific Characters—Head spindle-shaped, an occipital tentacle posteriorly ; eyes two 
pairs, arranged nearly in a transverse line. Peristomial segment forms a translucent lobe 
on each side, grooved ventrally. Tentacles short, thick, deep chocolate. Body resembling 
Spio, small, attaining its greatest width anteriorly, and gradually tapering to the slender 
tail, which ends in a bilobed flattened process. ‘The first setigerous segment carries only a 
ventral tuft of capillary bristles. The second foot has a dorsal lameila fused with the branchia, 
and longer dorsal bristles. The ventral lamella bears shorter capillary bristles. Shorter 
bristles with wide and dotted tips and striated shafts occur both dorsally and ventrally 
after the tenth foot. Bifid winged hooks appear in the ventral division about the fifteenth 
foot, with a large main fang, which leaves the neck nearly at a right angle, and has two 
spikes in lateral view on the crown above it. 
SYNONYMS. 
1914. Nerinides tridentata, Southern. Proc. Roy. Irish Acad., vol. xxxi, No. 47, p. 98, pl. x, 
fig. 23 a—4J. 
1915. 5 a McIntosh. Ann. Nat. Hist., ser. 8, vol. xv, p. 2. 
1922. FF 3 1d ems loid sera OVO ix 1.20: 
Habitat.—Blacksod Bay in Laminarian roots (Southern). The snout is pointed, with 
a median ridge, which in lateral view forms two divisions—an anterior less elevated, and a 
posterior terminating in the more or less adnate tentacle. In the line between the two 
divisions are the four black eyes arranged in a transverse row. The mouth opens inferiorly, 
and the extruded proboscis is bell-shaped and smooth. ‘The tentacles were absent in the 
example kindly sent by Mr. Southern, but he describes them as “ short, thick, and firmly 
adherent, of a deep chocolate colour.” 
The body is nearly an inch in length (16é—20 mm.) in life, tapered a little in front and 
more distinctly diminished posteriorly, where it terminates in two small rounded lobes, 
a slight dorsal process indicating the upper edge of the anus. Segments 61—70 short 
anteriorly, wider in the middle region. Dorsal surface flattened, ventral rounded. 
The first foot has a small conical papilla or cirrus, and a single (ventral) tuft of trans- 
! “Compt. Rend.,’ clxv, p. 284. 
