POLYCH/ETA FROM NORTH AMERICA. 805 



EXPLANATION OF THE PLATES. 



PiAXE LXXXVII. 



Fig. 1. Serpula columhiana from left side, X §. 



Fig. 2. Crucigera eygoylwra, anterior end froni right side, X 2. 



Fig. 3. Crucigera irregularis, whole animal from right side, X 2. 



Fig. 4. Apomatus timsii. 4 a, whole aiiiuial from the right side, X 3, d.g., dorsal 

 tenuinal gland; 4 S, collar seta, X 300; 4c, biaded sickle-sluiped seta 

 from thorax, X 300; 4cZ, crumpled anterior abdominal seta, X 300; 



4 e, short posterior abdominal, seta X 300 ; 4/, thoracic uncinus, X 300. 

 Fig. 5. Frotula pacijica. 5a, ventral view, X |-; oh, thoracic seta, X 300; 



5 c, anterior abdominal seta, embedded up to the dotted line, X 200 ; 

 5 d, short posterior abdominal seta, X 300 ; 5 e, tip of long posterior 

 abdominal seta, X 300 ; 5/, abdominal uncinus, X 300. 



PlATE LXXXVIII. 



Fig. 6. CMtinopoma greenlandiea. 6«, dorso-lateral view, X 2; 66, collar seta, 

 X 460; 6 c, abdominal seta, X 460; Qd, transverse section through 

 pedicle of operculum, v.s. stem of vesicle, X 55 ; 6 e, transverse section 

 through operculum showing vesicle (u) suspended in a loose connective 

 tissue, X 48. 



Fig. 7. Spirorbis vitreus, collar seta, X 220. 



Fig. 8. Spirorbis spirillum. 8 a, tube of discoid variety, X 48 ; 8 b, tube of 

 ascending variety, X 10 ; 8 c, collar seta, X 200. 



Fig. 9. Spirorbis pusilloides. 9 a, collar seta, X 460 ; 9 b, large abdominal seta, 

 X 460. 



Fig. 10. Spirorbis amb Hater alis. 10 a, collar seta, X 220; 10 5, calcareous plate 

 of operculum, lateral view, X 48 ; 10c, seta from 3rd thoracic segment, 

 showing fringed sickle-shaped extremity; 10 c?, ordinary biaded sickle, 

 fi-om 4th segment (twisted end) ; 10 e, brush-like abdominal seta, c-e, 

 X 220. 



Plate LXXXIX, 



Fig. 11. Spirorbis racemosus, sp. n. 11 a, collar seta, X 220; 11 J, calcareous plate 

 of operculum, X 48; lie, seta from 3rd thoracic segment, X 460; 

 11 d, dorsal view of whole animal showing stalked brood-pouch, X 12. 



Fig. 12. Spirorbis asperatus, seta from 3rd thoracic fascicle, X 460. 



Fig. 13. Spirorbis validus, collar seta, X 460. 



Fig. 14. Spirorbis medius, sp. n. 14 a, collar seta showing shallow posterior 

 notch, X 460. 14 5, ordinary capillary seta from 1st fascicle, X 460. 

 14 c, calcareous plate of operculum, dorsal view, showing talon and 

 lateral wings, X 16. It;^, latero-ventral view of opercular plate, 

 showing flat talon with lateral wing-like projections, X. 16. 14 e, ser- 

 rate:! biaded sickle, X 460. 



Fig. 15. Spirorbis latigerhansi, collar seta, X 460. 



Fig. 16. Spirorbis morclii. 16 a, collar seta, X 220. 16 5, operculum containing 

 ova, lateral view, X 48. 16 c, narrow seta of 2nd and 3rd fascicles, 

 X 220. 16 d, seta from 3rd fascicle, X 220. 



Proo. Zool. Soc— 1912, No. LIV. 54 



