364 PROCEEDINGS OF THE ACADEMY OF [June, 



oareous part, however, is remarkable, being built up of 3 or even 4 (a) 

 calcareous disks of complex form (6). Each has a somewhat grooved 

 rim with thin projecting flanges whose margins appear to be entire 

 when perfect, but are usually jagged as a result of wear. It is very 

 seldom that more than the basal disk and the one next beyond are 

 found entire. An excentric opening prolonged into a tube on the 

 proximal side perforates each disk obliquely dorsal to the center and 

 accommodates the siphuncular ligament, binding all together. The 

 number of branchia; is about 11, but could not be definitely ascertained, 

 owing to their being so closely matted together. 



There are 3 thoracic and about 24 setigerous abdominal segments, 

 the latter region being veiy short. The winged collar setffi have the 

 form shown at c, the basal fin being very long, uniform!}^ serrated and 

 overlapping the base of the blade without an interval. The blade is 

 very finely serrated, long, acute, and tapering. The remaining thoracic 

 setae are partly limbate capillary and jjartly serrate and sickle-shaped. 

 Each fascicle of abdominal setae contains but two, one being a minute 

 aciculum wdth the end bent, the other having a broadly expanded end 

 much like those of S. spirillum (d) . Nothing distinctive can be detected 

 about the uncinial plates. 



The type is No. 80, collection Academy of Natural Sciences of Phila- 

 delphia, and was taken along Math several cotypes at Dutch Harbor, 

 Unalaska, by Dr. Benjamin Sharp. Attached to a tough alga frond. 



