STREPTOSYLLUIS. 453 
PIONOSYLLIS SERRATA, Southern, 1914. Plate CX XXV, fig. 10—bristle. 
Specific Characters—Head rounded in front, straight behind; six eyes, the anterior 
mere specks at the bases of the lateral tentacles, the middle large with the lenses directed 
forward, the posterior nearer each other and the lenses directed backward. Median tentacle 
arises in front of the eyes ; lateral tentacles spring from the anterior margin. Palps ventral, 
fused at the base. Tentacles smooth and cylindrical, joimted at the base. Body minute, 
2°5 to 3 mm. long, with twenty-seven setigerous segments, which are widest at the tenth. 
It tapers posteriorly, the anal segment rounded and furnished with two slender subulate 
cur. Buccal segment invisible from the dorsum, being covered by the first setigerous 
segment. It bears a pair of tentacular cirri on each side, the dorsal pair being the longer, 
and like the tentacles smooth and cylindrical. The dorsal cirri of the first setigerous segment, 
which projects forward alongside the head, are the longest of all the appendages. In the 
anterior and posterior segments the ventral cirri extend beyond the setigerous lobes, but in 
the middle they are equal or slightly shorter. Foot with a bluntly poimted setigerous lobe, 
bearing a small dorsal papilla at the tip, so that it seems slightly bifid from above; ventral 
cirrus broad and pointed. The bristles form a fan-shaped series ; ends of the shafts swollen 
and bevelled, with conspicuous spines, the upper with long terminal pieces having four or 
five long slender teeth inferiorly ; tip boldly hooked, the process beneath almost vertical. 
ventral bristles simply hooked, and the margin is smooth or very faintly spmous. Of the 
sixteen bristles in each foot five to seven of the dorsal are bifid, the rest simple. Hach foot 
has one spine except the first, which has two, tapering distally and with a bulbous tip. In 
the six posterior segments is a long capillary bristle dorsally. 
SYNONYMS. 
1914. Pionosyllis serrata, Southern. Proc. Roy. Irish Acad., vol. xxxi, No. 47, p. 23, pls. m1 and iv, 
figs. 5 A—E. 
1921. 5 a McIntosh. Ann. Nat. Hist., ser. 9, vol. viii, p. 305. 
Habitat.—Between tide-marks, Blacksod Bay, Bofin Harbour, 1—4 fathoms, Ballynakill 
Harbour 2—8 fathoms, midwater net off Cleggan Head at 7 fathoms, and in the surface net 
off Inishturk (Southern). 
This form, according to Southern, is closely related to Pronosyllis pulligera, Krohn, 
differmg, however, in so far as the buccal segment is visible dorsally : the proventriculus 
extends only into two segments, and the spine and the bristles (Plate CX X XV, fig. 10) differ. 
The lateral tentacles are also shorter. 
As in the other minute forms further investigation may show different relationships. 
Syllis (Lyposyllis) varregata, Grube, again, which Southern distinguishes from P. prolifera 
by its colour-pattern, has the tips of bristles less boldly bifid, and the edge more serrate; whilst 
the spines in the posterior feet are very thick and bluntly pointed, especially in young 
specimens. This is a widely distributed species, ranging to Australia (Haswell) and elsewhere. 
Genus STREPTOSYLLIS, Webster & Benedict, 1887. 
Syllidee with three tentacles; four tentacular cirri; palpi fused at the base, filiform 
at the tip; cirri smooth or indistinctly moniliform. Proboscis unarmed ; feet in a variable 
