248 PROCEEDINGS OF THE ACADEMY OF [April, 



to one-third the body width, the longest ones in the neighborhood 

 of somite CC reaching easily beyond the middle line; in the posterior 

 region they continue nearly to the pygidium and as far as the last 

 one hundred segments reach to the median line. 



Acicula anteriorly are three or four, stout, tapered, chiefly very dark 

 brown, the dark tips exposed, blunt, somewhat oblique but not knobbed. 

 Posteriorly there are but two and finally one, and except that they 

 become more slender there is no change in form. 



Setse are of two forms: simple supra-acicular and compound sub- 

 acicular. No pectinate setse are visible in any of the preparations. 

 Simple seta? have long, slender shafts, dark colored toward the base, 

 but pale distally; they project prominently, the ends being slightly 

 doubly curved and gently tapered to very slender acute tips with a 

 faint marginal fringe but no distinct limbus. Somite III bears only 

 three or four simple setse, the number increasing to about twenty on 

 X. Behind C the number again diminishes, but the setse become first 

 longer, then very few and of small size on the caudal segments. Com- 

 pound setse (PL VII, fig. 5) are enlarged toward the distal ends of the 

 shaft which bears a few small marginal teeth, the appendage broad, 

 bidentate and slightly hooked distally and provided with a fringed 

 guard, its length one and one-half times width of enlarged end of 

 shaft and remarkably uniform on all parapodia. They are absent 

 from III and numerous by X, on which they form rows extending 

 anterior to and below the acicula. Farther back they undergo changes 

 similar to those affecting the simple setae. 



Mandibles (PI. VII, fig. 6) large, very hard, the horny carriers 

 yellowish with dark lines, very thick and firm, with an angular ridge 

 running the entire length. Jaw plates very large, white, calcareous, 

 of stony hardness, each plate bent nearly into a semicircle at the free 

 margin which is faintly denticulated, the dorso-lateral angle freely 

 projecting. Maxillse (PI. VII, fig. 7) deep brown, hard. Carriers of 

 forceps jaws broad with lateral emarginations and the two halves 

 closely united except at the caudal end; forceps with broad bases 

 marked by three longitudinal ridges, no masticatory teeth and short, 

 strongly hooked ends. Second pair (II) massive with four stout teeth 

 on the left and three and a rudimentary fourth on the right side. 

 Three accessory jaws (III, IV, V) each with a single tooth on the 

 left side arranged in a semicircle and two, one with two teeth, the 

 other with a single tooth, on the right side. 



Color of anterior end deep, iridescent purple, posterior reproductive 

 region of male pale brown, of female greenish drab with white rings. 

 Ventral phototactic organs brown. 



