TEREBELLIDAE 185 



Specific characters. No eye-spots. Ventral surface of first segment forms a lower 

 lip. In the anterior region the segments are rather indistinctly subdivided into secondary 

 rings. Small, rectangular ventral gland shields continued to the hinder end. Four pairs 

 of nephridiopores of which the three hinder pairs are very large and conspicuous. 

 Nephridia in the third, fourth, fifth and seventh segments {vide Hessle). The present 

 specimen is damaged and in poor condition. 



Subfamily TRICHOBRANCHINAE 



Cephalic lobe not enlarged. Branchiae filiform. Thoracic and abdominal uncini of 

 two distinct types. Thoracic uncini aciculiform, abdominal uncini pectiniform or 

 avicular. 



Genus Octobranchus, Marion and Bobretzky 



The head carries only one kind of tentacle dilated at the extremity. Four pairs of 

 simple filiform branchiae. Anterior segments carry membranous collars on the lateral 

 and ventral surfaces. No ventral gland shields. Dorsal bristles capillary. Thoracic 

 hooks with very long shafts, arranged in sessile tori. Abdominal hooks small, pectini- 

 form, carried by prominent rectangular pinnules. 



Octobranchus antarcticus, n.sp. (Fig. 33 a-g). 

 Occurrence. St. 182 (i). 



Specific characters. The single specimen is a ripe female measuring 17 mm. by 

 2 mm. for 28 chaetigers. The hinder end is damaged and I cannot tell whether the 

 specimen is complete. The tentacles are lost and all the gills except the left member 

 of the fourth pair. In spirit there is no colour. The head has a horseshoe-shaped upper 

 lobe without folds and ventral cushions. Dark brown eye-spots are present in a band. 

 The buccal segment sends forward a stout under-lip. The second segment sends for- 

 ward below the under-lip a ventral lappet with an uneven lobate edge. The third forms 

 a pair of more or less spatulate ventro-lateral lappets joined by a low fold across the 

 ventral surface. The fourth and fifth segments form enormous lateral and ventral collars, 

 open dorsally. The 6th segment forms a pair of relatively small, rounded lappets at the 

 sides of the body below the notopods (Fig. 33 a). 



There are 16 thoracic chaetigers. The first notopods are on the fifth, or last branchiate, 

 segment. The uncini begin on the fourth chaetiger or eighth segment. There are no ventral 

 gland shields. The single branchia consists of a stout basal column surmounted by a 

 filiform tip. The scars indicating the place of attachment of the three additional pairs 

 of branchiae are visible on the second, third and fourth segments. As I wish to leave 

 the only remaining branchia in place I am unable to examine its structure in detail. 



The bristles are borne by prominent notopodial lobes (Fig. 33/) with two lips. They 

 are of two kinds: (i) very delicate and transparent short capillary bristles (Fig. 33 c); 

 (2) larger bristles with narrow borders and long hair-like tips (Fig. 33 ^). Both kinds 

 are smooth. In the thoracic region the uncinigerous tori are sessile, but in the 

 abdominal region they are from the first abdominal segment borne on prominent 



