392 THE ANNELIDA POLYCHAETA. 



SCALIBREGMA INFLATUM H. Rathke. 



Nova acta Acad. Leop.-Car., 1843, 20, p. 184, pi. 9, fig. 15-21; Ashworth, Quart, journ. micros, sci., 



1902, 45, p. 238. 

 Oligobranchus roseus Sars, Fauna litt. Norveg. 1846, 1, p. 91, pi. 10, fig. 20-27. 

 Oligobranchus (,roenJandicus Sars, Ibid., p. 92. 

 Sccdibregma roseum Sars, Nyt mag. naturv., 1853, 7, p. 381. 

 iScalibregma inflatum corethusa Michaelsen, Gronliind Annel., 1898, p. 127 (epitoke). 



Locality. Between Unalaska and Kadiak : Sta. 3337 (lat. 53° 55' 30" 

 N., long. 163° 26' W.). Depth 280 fms. Bottom temp. 39.3° F. 27 August, 

 1890. One specimen. 



This is a widespread species occurring on both sides of the Atlantic in north- 

 ern latitudes, and also in the northern Pacific, as well as in the far southern lati- 

 tudes, such as the region about Prince Edward Island, Kerguelen, Strait of 

 Magellan, and New Zealand. 



Arenicolidae. 



In these annelids the body is elongate and cylindrical, is composed of numer- 

 ous somites, and presents either two or three more or less distinct regions. Colors 

 commonly greens or reds, with often superficial iridescence. The skin is charac- 

 teristically tesselated, consisting of a thin cuticle covering a thick glandular 

 hypoderm. 



Prostomium small, or but moderately developed. Nuchal grooves posteri- 

 orly. No tentacles or palpi. Eyes primitive and indistinct. 



The peristomium in most species bears a pair of otocysts. It is fused with 

 a somite that early becomes achaetous. 



In the setigerous region of the body each somite, excepting the first three, 

 is composed of five distinct annuli excepting in Branchiomaldane, in which but 

 two annuli are found. 



The parapodia are obviously biramous, each presenting a conical noto- 

 podium bearing ordinary setae and a transversely thickened neuropodium bear- 

 ing crochets. 



Branchiae always absent from the first seven somites, and often from more. 

 They are highly characteristic structures attached dorsally just mesad of the 

 bases of the notopodia. Each is a hollow outgrowth which is highly branched 

 in either a dendritic or pinnate manner, or the branches radiating from a common 

 point like the ribs of a fan. The gills often more or less retractile. 



Setae of the notopodia are all of the simple capillary type, smooth proxi- 



