456 SYLLIS (KHLERSIA) FERRUGINEA. 
segments; forty-five rows of dots—-jomed by wavy lines; passes into wide stomach with 
two diverticula in front. Anterior feet with bluntly rounded, bifid setigerous lobes; ventral 
cirrus massive, swollen at the base ; thirteenth segment has a fan-like series of bristles with 
curved shafts, the ends of which are enlarged and spinous; distal pieces with simple curved 
tips; spines large and thick, with swollen truncated tips. From the sixteenth segment 
they are replaced by slender spines. Capillary swimming-bristles on thirty-first foot. 
In the middle region of the body foot biramous, the dorsal division having a tuft of capillary 
bristles, and a slender spine with a blunt and rounded tip ; ventral division with a single 
upper winged bristle; four or five compound and a single simple bristle without wings 
below. Resembles O. morena, Langerhans, but differs in the structure of the simple winged 
bristles, and the thick spines of the anterior segments approach closely those of Streptosyllis, 
which, however, has an unarmed proboscis. 
SYNONYMS. 
1914. Opisthodonta pterocheta, Southern. Proce. Roy. Irish Acad., vol. xxxi, No. 47, p. 30, pl. iv, 
figs. 6 a—@. 
1921. is A McIntosh. Ann. Nat. Hist., ser. 9, vol. viii, p. 306. 
Habitat.—Procured in the midwater tow-net off Cleggan Head, Co. Galway, in October 
(Southern). 
Fig. 171.—Anterior region of Opisthodonta pterocheta showing the tooth about the middle of the pharynx. 
x 42. After Southern. 
In this form, an imperfect male of which was obtained in July, the sharp tooth is 
situated behind the middle of the pharynx. Capillary swimming-bristles commence on 
the thirty-first segment. In the middle region of the body the foot is biramous, the 
dorsal division having a tuft of long capillary bristles and a slender spine with a bluntly 
rounded tip. Development is probably direct (Southern). The thirteenth foot is shown 
in Plate CXX XVII, fig. 4. 
SYLLis (HHLERSIA) FERRUGINEA, Langerhans, 1881. Plate CXXXVIII, fig. 7—tips of 
bristles. 
Specific Characters—Head with broad palpi; four large posterior eyes, and two smaller 
anterior ; tentacles with seventeen to twenty-five segments ; tentacular cirri seventeen to 
twenty-four segments. Body of immature example 1:0 cm. long, with seventy segments, 
reddish, with greenish mtestine. Dorsal cirri of the second segment with thirty articulations, 
