AMPHICTENIDAE. 461 



The uncinigerous tori begin on the fifth setigerous somite. Both ends of 

 the tori project freely over the base. The anterior tori are longest, the others 

 decreasing rapidly caudad. The uncini are in a single series. The abdominal 

 tori are very short, flattened, the ends projecting beyond the base, but not 

 angular. Above is a short, cylindrical notopodial process, and between this and 

 the torus a very long and slender cirrus. (Plate 76, fig. 9). 



The uncini in profile view present the general appearance usual in related 

 genera. Above the short, rounded, inferior process is a dwarf, erect tooth, and 

 above this four larger, uncinate teeth which decrease in size toward the crest. 

 In frontal \'iew it is seen that there is at the apex a transverse series of tlii'ee 

 teeth, below this a second series of three, then one of two, while the lowermost 

 tooth is single. The usual formula, beginning with the reduced lower tooth, 

 is thus 1+1+2+3+3. (Plate 77, fig. 10). 



The setae of the type, at their maximum, extend about 2.1 mm. distad of 

 their tubercles. They are very dilute j'ellow in color. Distally they gradually 

 narrow to long, slender tips, and are narrowly biUmbate and strongly fibrillate. 



The tubes as preserved are from 150 to 200 mm. long and have a diameter 

 in the middle region of about 7 mm. They are composed of fine greyish black 

 mud, in which are to be detected the shells and shell-fragments of Globigerinae, 

 Radiolaria, and the frustules of diatoms. 



Locality. Between the Galapagos Islands and Peru: Sta. 4649 (lat. 

 5° 17' S., long. 85° 20' W.). Depth 2,235 fms. 10 November, 1904. Numer- 

 ous specimens in their tubes. 



Gen. et sp.? 



An ampharetid dredged off Panama (Sta. 3395) at a depth of 730 fms. on 

 11 March, 1891, is too defective and badly preserved for identification. 



Amphictenidae. 



These are small or medium sized polychaetes in which the body is divided 

 into two unequal and sharply distinct regions, the thorax and the abdomen, 

 or scape, the latter very short, being composed of but five or six achaetous 

 somites. The abdomen is convex beneath, but is dorsally fluted, or furrowed, 

 and bears at the caudal end a short, thread-like process, or cirrus. The thorax 

 is thick and subcyUndrical. Somites not distinctly separated excepting about 



