324 SERPULIDAL. 
Lamck., Galeolaria, Lamck.?, Ditrypa, Berk ?, Hyalopomatus (var. Marenzelleri), Chitinopoma, 
Lev. ? ; 
3. Hooks with more or less numerous teeth, more or less fine, terminating anteriorly 
in a large process convex dorsally, and hollowed ventrally like a gouge:—Gen. Pomatocerus, 
Phil., Sporobranchus, Blv., Pomatostequs, Schm. 
4. Hooks with a free border, thickened, rounded, and not denticulated, having transverse 
parallel striz, and terminated by a small enlargement in the form of a gouge':—Gen. Placo- 
stegus, Phil. 
5. Hooks with numerous and extremely fine denticulations, deeply hollowed anteriorly, 
and terminating at the other end by a curved spine (not grooved), sharper and longer than 
in the preceding type:—Gen. Protula, Risso (incl. Psygmobranchus, Phil.), Apomatus, Phil. 
The hooks keep to the same type anteriorly and posteriorly, though the latter may be 
smaller. It is otherwise with the bristles, which differ in the two regions of the body, and 
especially do those of the first segment differ. 
The peculiar bristles of the first segment only exist in fifteen genera ; in the others (Ver- 
nulia, Galeolaria, Ditrypa, Hyalopomatus, Pomatocerus, Protula, Apomatus) they do not differ 
from the other bristles of the anterior region. In the genus Placostegus only the first segment 
is devoid of bristles, which are replaced by a band of eyes. On account of this exception 
and because the bristles of the first segment vary in the same genus, Langerhans attributes 
only secondary importance to this condition, but the variations are also very great between 
the thoracic and the abdominal bristles. 
The peculiar bristles of the first segment fall under five types :— 
1. Massive bristles with a long terminal whip, preceded by two short cones:—Gen. 
Serpula, Hydroides, Crucigera. 
2. “ Kneed ” bristles in which the terminal blade is preceded by a “bite,” with a serrated 
edge:—Gen. Filograna, Salmacina, Filogranula, Spirorbis, Pileolarva, Protis, Chitinopoma, 
and Omphalopoma. 
3. “ Kneed” bristles without the “ bite,” and without its serrated edge :—Gen. Sprrorbis, 
Omphalopoma. 
4. Bristles indented in front of the terminal point, which is brush-like.* Gen. Spiro- 
branchus, Pomatostegus. 
5. Simple acicular bristles:—Gen. Omphalopoma. 
The thoracic bristles (other than those of the first segment) can be ranged under 
three types: 
1. Capillary bristles more or less winged :—Gen. Serpula, Hydroides, Crucigera, Vermila, 
Galeolaria, Spirorbis, Pileolaria, Pomatocerus, Spirobranchus, Pomatostegus, Ditrupa, Hyalopo- 
matus, Protula, Protis. 
2. Bristles in which the curved extremity is preceded by a wing in most of the thoracic 
segments :—Gen. Spirorbis, Vermilia, Omphalopoma, Apomatus. 
3. Bristles with a curved, serrated extremity without the wing preceding it:—Gen. 
Filograna, Salmacina, Filogranula, Spirorbis, Chitinopoma. 
The last segments of the abdomen generally bear simple capillary bristles in connection 
" Marenzeller, ‘Denks. K. Akad. der Wiss. Wien,’ Bd. Ix, p. 93, pl. iv, fig. 17 6. 
* Ehlers, ‘ Anne]. Blake.,’ vol. xv, 1887, pl. lvii, fig. 11, and pl. lviu, fig, 1. 
