SABELLIDKS AND SERPULIDES 24! 



SPIRORBIS INCONGRUUS sp. nov. 



PL XL, figs. 19, 20, 28. 



Type locality. Prince William Sound. 



Associated with the preceding, S. morchi, are smaller, similarly 

 coiled, but dextral tubes, slightly flattened on top, the surface rough- 

 ened by growth lines, and an ill-defined spiral line feebly indicating an 

 outer shoulder. 



Collar setae also similar to those in S. morchi. 



Calcareous plate in the operculum solid and somewhat resembling a 

 plug, thus differing from that of any other species. 



Diameter about 1.5 mm. ; height about i mm. 



S. rugatus found on stones at Sitka forms similar dextral tubes, but 

 the collar setae are finely serrate, tapered blades without any indication 

 of a fin-like base. 



Prince William Sound, at Orca, on Serpula tubes, and at Virgin 

 Bay, on Crucigera tubes. 



SPIRORBIS QUADRANGULARIS Stimpson 1853. 



pi. xxxix, fig. 37; pi. XL, figs. 10, n, 21, 23, 26, 30; pi. XLII, figs. 23-29; 

 pi. XLIII, figs. 14, 15. 



Type locality. Bay of Fundy, in 10 fathoms. 



Tubes found on Crucigera tubes from Alaska are not four-sided, 

 but have only a perpendicular inner wall with angular, seldom cari- 

 nated, shoulder defining a small central cavity. A similar form is 

 very common along the eastern coast, where there is found great varia- 

 bility in the development of the tubes. Young are often without the 

 slightest indication of any angularity, resembling S. spirorbis and 

 maturing into the form figured by Levinsen as S. affinis, which often 

 twists irregularly upward like S. lucidus; others develop a small 

 ridge on top of the whorls, which sometimes increases into a conspic- 

 uous carina forming three-sided whorls. Upon examination of speci- 

 mens this is found to be the form called S. granulatus by Moore 

 (1902) and is probably the one identified by Levinsen (1883) as the 

 S. carinatus of Montagu (1803). Until the animal of specimens 

 from England can be studied this question must remain undecided, 

 especially as there are in the Yale Museum, on a worn bivalve from 

 England, several sinistral, unicarinate, regularly coiled tubes, which 

 differ from the west Atlantic form in having a large central cavity 

 showing all the whorls, and may prove to be the true S. carinatus. 



All the animals examined agree in having a similar convex calcare- 

 ous cap on the operculum and the same form of setae, those of the col- 



