798 MISS HELEN PIXELL ON 



Sub-genus Protol.eospira, nov. 



1. Tube sinistral. 



2. Four complete setigerous segments to thorax. 



10. Spirorbis ambilateralis, sp. n. (PI. LXXXVIII. 

 figs. 10«-10e.) 



Specific characteristics : — 



1. Collar setae very large, conspicuously serrated blades with 



fin-like expansion at base (fig. 10 a). 



2. Operculum without brood-pouch. 



3. Talon of operculum with large hook-like process (fig. 10 b). 



4. Some setae of 3rd segment have fringed ends (fig. 10 c). 



5. Some setae of 4th segment ordinary bladed sickles. 



6. Abdominal setae brush-like (fig. 10 e). 



7. Dorso-lateral brood-pouch. 



Several specimens on the inner sides of shells of Balanus 

 nuhilus from Dodds Narrows, 15-25 fathoms. Tubes forming 

 translucent sinistral spirals measuring 3 to 4 mm. across. The 

 surface is distinctly corrugated outside, highly polished inside ; 

 the aperture measures 1 mm. in diameter. 



Bi-anchiae 12 — 6 on the right, and the operculum with 5 

 others on the left. The pinnae extend upwards and reach the 

 same height as the rachises. The opercular plate (fig. 10 6) 

 is very like that of S. cormi-arietis Marion & Bobretzky (15). 

 From close to the point of origin of the pedicle arises a wide tube 

 which passes across the dorsal surface beneath the left lateral 

 lobe of the collar, and enlarges into the thin-walled brood-sac 

 which lies along the dorso-lateral surface on the right side. This 

 structure has never, so far as I am aware, been described before : 

 it is figured and more fully described for S. racemosus, in which 

 species it was fii'st seen. 



Collar wide and entire ; the collar setae rather more than 1 mm. 

 in length (fig. 10 a). Setae of 2nd segment very numerous, all 

 with simple blades ; these appear again in the 3rd fascicle, and 

 with them some shorter bladed setae with their extremities more 

 or less curved and fringed (fig. 10 c). The setae of the 4th thoracic 

 segment are few in number ; on the convex side of one specimen 

 there w^ere three bladed sickles (fig. 1 d) and three with plain 

 blades. The uncigerous tori on the 4th segment are also smaller 

 than on the two preceding, especially on the right (convex) side. 

 The thoracic uncini are about 90 jj. long and have 20-25 teeth. 

 Those on the abdomen are only 25 jj, in length. About 50 of 

 the latter make up each of the tori which are very distinct on 

 the 18-20 abdominal segments : they begin quite close to the 

 posterior end of the thorax — the anterior asetigerous region of 

 the abdomen being very short. 



The collar setae in this form seem to have been specially 



