508 PROCEEDINGS OF THE ACADEMY OF [NoV. 



equal to their length and succeeding ones by a less distance. Pos- 

 terior to the region of ventral plates they become more elevated and 

 prominent, but, though assuming a lappet-form, they never become 

 largely free, even on posterior abdominal segments. 



The characteristic setae arise from short vertical lines in tufts of 

 about a dozen arranged in double series. They (fig. 16) have remark- 

 ably broad limbi, those of the posterior row being shorter than and 

 half again as broad as the one figured; the very slender and much 

 attenuated tip is very long, and the fringe nearly obsolete and confined 

 to the outer end on the long setse, but better developed, though 

 exceedingly delicate, on the short ones. 



Uncini occur in single series pointing forward on V-X, in double 

 series alternating in position and facing each other on XI- XXVIII, 

 then again in single series to the end ; there are about thirty-five on V, 

 sixty on X and XI, thirty-six on XVIII and twenty on L. They are 

 nearly colorless, with short, strongly convex bases deeply notched in 

 front, the beak stout, the crest of four transverse rows of 3-9 teeth 

 and the guard short and broad (fig. 17). 



Color pale reddish salmon, deepest anteriorly, tentacles flesh color. 



This species has been taken only on the piles of the New York Yacht 

 Club wharf in Vineyard Haven, where it occurs sparingly below low 

 water among Cynthia and Amaroecium; lives in small mud tubes and 

 breeds in early July. 



Explanation op Plate XIX. 



Arabella spinifera — figs. 1 to 7. 



Fig. 1. — Ventral view of maxillae, the accessory jaws slightly turned by 

 pressure. X 56. 



Fig. 2. — Dorsal view of mandibles. X 56. 



Fig. 3. — Outline of parapodium III, posterior aspect. X 56. 



Fig. 4. — Anterior view of parapodium X. X 56. 



Fig. 5. — Distal ends of the two acicula. X 250. 



Fig. 6. — Profile view of a moderately elongated seta from X. X 250. 



Fig. 7. — Face view of a short subacicular seta from X. X 250. 

 Praxillella tricirrata — figs. 8-12. 



Fig. 8. — Pygidium and caudal achaetous segments X 9 



Fig. 9. — Slender capillary seta from XI. X 250. 



Fig. 10. — Bipinnate capillary seta from XI. X 440. 



Fig. 11. — An entire crochet from XI. X 82. 



Fig. 12.— End of crochet. X 360. 

 Cirratulus parvus — figs. 13 and 14. 



Fig. 13. — Anterior end showing the brancliias and branchial cirri. X 24 



Fig. 14. — A tuft of notopodial cirri from the middle region. X 250. 

 Amphitrite attenuata — figs. 15 to 17 



Fig. 15.— First gill of the left side. X 24. 



Fig. 16. — A thoracic seta in | view. X 360 



Fig. 17. — A thoracic uncinus. X 360. 



