Chamberlin — Polychaetes from Monterey Bay. 179 



CAPITELLIM. 



27. Notomastus pallidior, sp. nov. 



In general form differing from N. tenuis Moore and agreeing with N. 

 angidatus Chamb. in having the thorax decidedly quadrate rather than 

 terete. No abrupt enlargement at beginning of abdomen, the thorax 

 passing gradually into abdomen. Contrasts strongly with N. angidatus 

 in color, being yellow instead of a dense green. Prostomium less strictly 

 conical than in angulatus, the palpoidal terminal division abruptly narrower 

 than the basal and distally rounded, the sides in ventral view convex; 

 surface not showing numerous fine points as usual in angulatus. Ventral 

 surface of peristomium with a large V-shaped impression formed by two 

 sulci arising from near anterior margin on sides and meeting at an angle 

 on the midventral line at the caudal margin. The peristomium subcy- 

 lindrical or only moderately narrowed cephalad, at anterior end abruptly 

 much wider than prostomium. Thorax composed of twelve setigerous 

 somites. All these clearly biannulate, the separating sulci strongly marked, 

 especially laterally; a longitudinal furrow along each side. Most thoracic 

 segment showing a vague division of anterior subsegment. Posterior 

 subsegments much shorter than the anterior, in the last segment only 

 half as long. None of the types is complete. The longest one has about 

 one hundred and thirty segments present, of which those in the middle 

 region are longer than wide. The total length of this specimen is 78 mm. 

 with a maximum width of about 1 mm. 



Several specimens were taken. 



SCALIBREGMIM. 



28. Sclerocheilus pacificus Moore. 



Proc. acad. sci. Phil., 1909, p. 282, pi. 9, f. 59. 

 One specimen. 



TEREBELLID.E. 

 29. Thelepus crispus Johnson. 



Proc. Boston soc. nat. hist., 1901, p. 428, pi. 17, f. 175-178b. 

 Common in this region. 



SABELLID.E. 

 30. Pseud opota mil la brevibranchia Moore. 



Proc. acad. sci. Phil., 1905, p. 555, pi. 37, f. 1-7. 



Numerous specimens of this species and their tubes are in the collection. 

 Some of these are variant in having the eyes almost or wholly obliterated. 

 One specimen has nine and one ten setigerous somites in place of the 

 usual eight. 



