170 THE ANNELIDA POLYCHAETA. 



Locality. Gilbert Islands: off Apaiang. Surface. Surface temp. 84° F. 

 3 January, 1900. Numerous specimens taken at night by electric light. 



This species in lacking any distinct markings as well as in limited number of 

 somites of the anterior division of the body presents resemblances to A. prolifer 

 O. F. Miiller, though numerous differences appear upon closer study. The palpi 

 present uniformly a strongly marked difference in being conspicuously geniculate 

 near the base, the organs distad of the angle extending directly ectad and pre- 

 senting a very characteristic appearance. The tentacular cirri are less smooth, 

 showing distinct evidence of numerous annuli. The minor tentacles are attached 

 nearer the middle line. The median tentacles and the tentacular cirri are much 

 longer. The number of somites bearing only composite setae is constantly 

 six. The main division of the body wholly lacks pigment, instead of being 

 yellowish. 



Atjtolytus planipalpus, sp. nov.^ 



Plate 20, fig. 4; Plate 21, fig. 1, 2. 



Epitokous Male (Polybostrichus) . 



The general color is yellow, excepting the blackish eyes and the anterior 

 seminiferous division, which is brown. The cirri, tentacles, and palpi are nearly 

 colorless, somewhat whitish. 



The body of the type consists of an anterior region of fourteen setigerous 

 somites, in which the setae are all of the coarse composite type and all of which 

 are crowded with masses of spermatozoa, and of a longer posterior region which 

 contains no sexual products and which has long, simple, natatory setae in addi- 

 tion to the coarse composite ones. The posterior region is regenerated posteriorly , 

 the more slender regenerated portion embracing twenty-four somites and the 

 anterior portion thirty-six less crowded somites, making a total of sixty for the 

 region. The total number of somites in the body is seventy-five, of which 

 seventy-four are setigerous. The total length is near 9.5 mm. 



The prostomium is transversely oblong, the anterior margin long and 

 straight. The palpi, or the fused palpi and paired tentacles, are strongly flat- 

 tened, thin, and very broad proximally. They extend along the upper surface 

 of the prostomium obliquely a little ectad of caudad to or beyond the pos- 

 terior eyes which are thereby nearly wholly covered. They are narrowed 



' planus, flat, aiitl palpus. 



