1905.1 NATURAL SCIENCES OF PHILADELPHIA. 555 



FIVE NEW SPECIES OF PSEUDOPOTAMILLA FROM THE PACIFIC COAST OF 



NORTH AMERICA. 



BY J. PERCY MOORE. 



A noteworthy portion of the Polychseta collections of the Alaskan 

 Salmon Commission of 1903 is seven species, five of which are herein 

 described as new. of the genus Pseudopotamilla recenth^ established 

 by Miss Bush. These new species are of interest in indicating the 

 interrelations of Pseudopotamilla and other genera into which the 

 former tends to grade. In most respects P. intermedia is most typical, 

 and stands between the other species, which may be grouped in couples 

 having quite distinct affinities. On the one hand P. hrevihranchiata 

 and P. occelata approach Eudistylia in the structure of the collar, and 

 the former especially in the uncini and the latter in the numerous eyes 

 and general habit. Neither of these, however, shows any indication 

 of spiral coiling of the branchial bases, which are small and simple. 

 On the other hand, P. splendida and P. anoculata have the angulated 

 branchial stems without eyes and the more elongated spatulate tho- 

 racic setfe which characterize Parasahella and Sabella, but the dorsal 

 collar lobes are exceptionally well developed and the branchial bases 

 are very small and simple. The first three species have the avicular 

 uncini of the posterior thoracic segments enlarged and otherwise pecu- 

 liar, in this respect resembling P. oculifera Leidy. 

 Pseudopotamilla brevibranchiata sp. nov. PL XXXVII, figs. 1 to 7. 



A species remarkable for the shortness of its branchise and the con- 

 spicuousness of its eyes. Two specimens containing nearly mature 

 ova measure 55 and 58 mm. long and have 128 and 151 segments 

 respectively. Of this length the palpi and branchial crown measure 

 only 6 to 6.5 mm. and the thorax 8 mm. Owing to the contraction of 

 the abdomen the form is rather short and stout, but the posterior -J 

 tapers in the usual way to the small pygidium, which bears a close 

 aggregation of small brown eye spots dorsal to the anus. 



The palpi or branchial bases are very firm and rigid, not at all pro- 

 duced ventrally nor spirally twisted, though slightl}- inflected and 

 winged ; the distal margin is even and transverse and the height uniform 

 (about 1.5 mm.) all round. The dorsal free margin bears a rather 

 prominent, rigid, slightly incvuved wing which overlaps its fellow 

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