SABELLIDES AND SERPULIDES 



229 



The very small Protula arctica Hansen 1882 was referred to the 

 genus Protis by Ehlers 1887 (type, Protis simplex). The uncial 

 plates have but a few (6) coarse teeth, and the collar setae have a dis«- 

 tinct basal expansion or fin. There is no operculum. 



HYALOPOMATOPSIS OCCIDENTALIS sp. nov. 



p1. XL, figs. 3, 22 ; pi. XLIV, figs. 2, 4, 8, 9. 



Type locality. — Virgin Bay, Prince William Sound. 



Small, thick, white, calcareous, angular, more or less curved tubes, 

 with a prominent median keel, were attached to tubes of Serpula 

 splendens. They strongly resemble the figure of the tube of Chitin- 

 opoma greenlandica (Morch)^ given by Levinsen in 1883 as C. fab- 

 ricii (Serpula triquetra Fabricius non Linne). 



The colorless animal also has a long, slender, rounded form similar 

 to Levinsen's figure. 



The branchial lobes are small, not prolonged ventrally, nor involute, 

 and bear 6 pairs of long branchi^, their rachises broad at base and 

 furnished on their inner surfaces with long, graduated, ciliated pinnse 

 not extending to the end but leaving a long, unadorned, terminal por- 

 tion ; an additional smaller undeveloped branchia is on the end of the 

 lobe opposite the one bearing the operculum. This is a small, elon- 

 gated, semitransparent bulb on a very long, slender peduncle, often 

 covered on the end with delicate algiE (p1. xliv, fig. 8), in the adult 

 specimens usually showing an inner sphere (air bubble.?). 



No thoracic membrane. 



Collar very deep, with deep lateral clefts. 



There are about 60 segments, of which 7 belong to the thorax, where 

 the fascicles of setae form straight series and the tori are short. 



^ Mdrch in 1863 referred the Serpula triquetra of Fabricius 1780 to Hydroides 

 norvegica as var. gronlandica, which Malmgren in 1867 separated as a distinct 

 species, referred to Hydroides with doubt, so that Levinsen's name fahricii is 

 superfluous. 



Specimens attached to stones from. Greenland and to the tubes of Notkria 

 conchylega from 32 fathoms off the New England coast are in the Yale University 

 Museum, and may prove to be the same as those on the same host from Green- 

 land identified by Moore ( 1902) as Serpula sp. ; these could not be compared. 

 The operculum (pi. xxxvii, figs. 3, 9) is covered by a thin chitinous cup-like plate, 

 and has not the bulb-like form of the western species. When stained and 

 mounted in glycerine, a central chamber with connecting peduncle-canal was 

 distinctly revealed, which differs from that in the opercula of Spirorbis in having 

 three distinct parts, those above and below the central chamber or cavity being 

 filled with animal matter. See also pi. xl, fig. 31. 



