204 BUSH 



Oral membranes as in Potamilla and related genera ; one extending 

 inward from each side of the ventral fissure, along the base of each 

 branchial lobe, folding on itself to the ventral end of the lobe ; the 

 other, inside this, more or less irregular, leaf-like in form, supporting 

 long, slender, tapered, dorsal ends. 



Fascicles of the seta small, laterally elongated, in straight series ; 

 thoracic tori comparatively short, of about uniform length. Inferior 

 thoracic setae, back of the collar fascicle, spatulate in form. 



Miiller 1771, as Amphitrite, Leuckart 1849, as Sabella, Quatre- 

 fages 1865 and Mclntosh 1868, as Sabella saxicava, Malmgren 1867 

 -f- Marion and Bobretzky 1875 -f- Marion 1878 -j- Langerhans 1884 

 -f- Andrews 1891 and Saint -Joseph 1894, as Potamilla, have published 

 figures of this species, but as there appears to be considerable variation 

 in the form of the setae, especially the uncini, it is probable that the 

 name has been sometimes erroneously applied. 



In this genus can be placed Potamilla ocultfera Leidy (1855), 

 which has long been considered synonymous with P. reniformts. 

 Figures of the characteristic seta? of specimens (NO. 885 Yale Mu- 

 seum), collected at Watch Hill, Rhode Island, are given on pi. xxxiu, 

 figs. 6, 30; pi. xxxiv, fig. ii ; pi. xxxvn, figs, n, 13, 14, 29. Pota- 

 milla tortuosa Webster (1878), from the Virginia coast, has similai 

 inferior thoracic setae, and may possibly belong here. Mclntosh 

 (1885) thought this identical with the species from Torquay identified 

 by him as Sabella saxicava. Pseudopotamilla reniformis (Miiller) 

 was recorded from Bering Sea by Marenzeller (1890). 



PSEUDOPOTAMILLA DEBILIS sp. nov. 

 pi. xxxvi, figs. 23, 24, 26. 



Type locality. Pacific Grove, California. 



A long, slender, delicate, nearly colorless specimen, has only faint 

 indications of brown along the distal portion of the branchiae, which 

 number about 16 in each lobe and are very long (about 7.5 mm.) and 

 very slender, with long, delicate, well-separated pinnae and a few 

 scattered eyes. 



The collar has very wide dorso-lateral notches and long, narrow, 

 pointed, ventral ends. 



There are 8 thoracic and over 50 abdominal segments (extremity 

 mutilated) . 



Length of thorax along setae about 4 mm. ; breadth about 2.5 

 mm. 



