1904.] 



NATURAL SCIENCES OF PHILADELPHIA. 



177 



from a short peduncle, which is apparently differentiated from the 

 longitudinal ventral muscular layer of the body-wall and separated 

 from the branchial lobes. 



Thoracic setae simple tapered blades with but little color in 

 three fascicles on each side with two series of uncini. Those on the 

 collar (fig. e) somewhat broader and less regularly tapered than the 

 others; no odd ones found in the second or third bundles. Uncini 

 distinctly yellow or delicate horn-color with numerous fine teeth, 

 clearly seen under a 7 objective, those on the abdomen much shorter 

 and associated with a single similarly colored seta. 



Two specimens on one of the red algae with S. argutus, at Station 

 3,730, in 34 fathoms. May 16, 1900. 



Figs, c and d. S. foraminosus, front and rear 

 views of operculum, filled with eggs. 



Fig. c. S. foraminosus, 

 seta from collar fascicle. 



Spirorbis bellulus Bush sp. nov. 



Tube small, regularly coiled, dextral, with small central cavity, the 

 rounded whorls ornamented with three, sometimes four, unequal, 

 rounded threads, the one on the summit being more prominent than 

 the others. 



Specimens from 1 to 1.5 mm. in diameter. 



Branchiae peculiarly developed, probably abnormal, broad, thin, 

 flattened, with few pinnae. Operculum 

 (figs. / and g) on a very long peduncle, 

 with somewhat squarish calcareous plate 

 with deep erect thickened rim. 



Setae (fig. h) long and slender simple 

 blades, similar in all the fascicles which 

 are three on each side of the thorax 

 with two series of uncini, those on the 

 collar showing a few comparatively 

 12 



Figs. / and g. S. bellulus, 

 operculum, front and rear 

 views. 



