SABELLIDES AND SERPULIDES 



203 



Length about 46 mm., or 1.6 inches; breadth 5 mm,; length of 

 thorax along setas about 5 mm. 

 Kadiak, July 3, one specimen. 



Genus Potamilla Malmgren 1865. 

 Type, Potamilla neglecta (Sars). 



The genus Potamilla of Malmgren appears to have been rather 

 vaguely used by subsequent writers. It w^as proposed in 1865 for the 

 species Sabella neglecta Sars ( 1 85 1 ) , redescribed and figured as the 

 first species, and Potamilla torelli Malmgren, vs^hich are readily dis- 

 tinguished, especially from species of Sabella^ by the bilobed collar 

 meeting at the dorsal furrow and by shorter, broader, subspatulate^ 

 inferior thoracic setas ; their borders, however, being equal, not 

 unequal as given by Malmgren. 



It was also suggested that Sabella reniformis (Miiller) Leuckart 

 might be referable to the same genus, but the excellent figures given in 

 1867 show a marked difference in the four-lobed collar with deep 

 dorso-lateral incisions or notches, as well as in the shorter, spatulate 

 inferior thoracic setae. The new name Pseudopotamilla is therefore 

 proposed for such forms. 



All species hitherto referred to Potamilla need much careful study 

 before their correct relationship can be determined. Potamilla 

 malmgreni Hansen (1882) from N. L. 63-65° + , W. L. 5-7° +, in 

 1 163-12 15 fathoms, should be referred to the genus Potamis Ehlers 

 (1887).^ The avicular thoracic hooks are somewhat analogous in 

 form to those in Euchone, 



Genus Pseudopotamilla nov. 



Type, Potamilla reniformis (Miiller + Leuckart) Malmgren. 



This generic name is proposed for species similar to P, reniformis 

 which have hitherto been referred to the genus Potamilla, 



The branchial lobes are simple, and not prolonged ventrally, but 

 differ from those in Potamilla in having the dorsal ends protected by 

 a stiff, sharp or thin edge, often turning outward. Malmgren's figure 

 77A, p1. XIII, 1867, is not sufficiently clear to show this. 



The collar is four-lobed, meeting on the back, with small, angular, 

 dorsal lobes formed by conspicuous dorso-lateral incisions or notches, 

 and more or less developed, usually pointed, ventral ends. 



*Type, Potamis spatJiiferus Ehlers, from off the coast of Florida, in 275 

 fathoms. 



