200 BUSH 



prolonged ventrally, with the branchiae not so distinctly four-sided, and 

 connected by a very slightly developed, posterior, interbranchial, mem- 

 branous web. The collar bilobed, without lateral incisions, widely 

 separated on the back, ending in more or less angular ventral ends. 



All the fascicles of setae laterally elongated. 



Setae on the thorax of two forms ; superior ones long, regularly 

 tapered ; inferior ones shorter, broader, and oblanceolate. Tori with 

 avicular uncini and pennoned setae. 



Sabella microphthahna Verrill (1874) from the southern coast of 

 New England is a Parasabella. 



PARASABELLA MEDIA sp. no v. 



pI. XXVII, figs. 3-5; p1. XXXIII, figs. 34-36; p1. XXXIV, fig. 3; pi. xxxvi, figs. 



13, 14; pi. XXXVII, fig. 30. 



Type locality. — Kadiak. 



This small species is short and stout, abruptly tapered near the broad 

 posterior end, light brown in color, tinged with crimson, with the 

 branchiae variously spotted with dark brown. 



Segments about 100 in the largest example, of which 8 belong to the 

 thorax, on which the fascicles of setse form oblique series. 



Branchial lobes but slightly prolonged ventrally, bearing about 18 

 pairs of long, rather slender, much curled and twisted branchi^ ; their 

 rachises not so distinctly four-sided as in Sabella^ and not connected 

 by a noticeable basal membrane or web ; pinnae short, but little devel- 

 oped, leaving long tapered ends. The irregular development of the 

 pinnae and the curling of the branchiae are largely, if not entirely, due 

 to the presence of a curious parasite which attaches itself to, and 

 develops in masses along, the thin inner membranous edges of the 

 rachises. These masses are protected by a thin transparent wall. 

 Eyes none; not discernible in preserved specimens. 



Collar well developed, without lateral incisions, open on the back, 

 arising abruptly midway between the broad dorsal furrow and the first 

 fascicle of setae, ending in small, angular, ventral lobes. 



Set£e characteristic of the genus, with the exception of the pennoned 

 ones of the thoracic tori, which have one side larger than the other, and 

 developed into a long, slender, terminal filament, which is separated 

 or split at its base, from the pointed end of the shaft or manubrium. 



Length of largest specimen about 35 mm. ; breadth at base of thorax 

 about 5 mm, ; at base of collar 4 mm. ; length of thorax along setze 

 about 5.5 mm. Length of smallest specimens 19 mm.; breadth at, 

 base of thorax about 4 mm. 



