1906.] NATURAL SCIENCES OF PHILADELPHIA. 241 



stitutes its greater part, a circle of twenty-three separate and distinct 

 cirri, all of which are slender, regular and equal, and not, as in many 

 species of the genus, alternately longer and shorter. Apparently they 

 increase slightly in size from the dorsal to the ventral side; and the 

 median ventral one is much elongated, its length equalling that of the 

 four achaetous segments combined or about ten times the length of the 

 other marginal papillae, and it is very slender distally. 



On the first three setigerous somites (II to TV) about thirty seta? 

 occur in each group and are disposed in small vertical tufts just above 

 the lateral line and about one-third of the length of the somite from 

 its anterior end. The small number of uncini (3 to 5) are sessile in 

 short, transverse lines just below the seta?. On succeeding segments 

 the setae are more numerous and project upward and outward in tufts 

 from small tubercles. The uncini are more numerous (13 on Y, 20 

 on IX, and still more posteriorly) and form longer lines widely separ- 

 ated below by a space of twice or more their own length. The tori 

 have become prominent swellings. On IX they have become trans- 

 ferred to the posterior end, although the boundary between this seg- 

 ment and VIII is not clearly defined. This condition of the tori con- 

 tinues throughout the body, though they become even more prominent 

 posteriorly and are united across the dorsum of each segment by a 

 glandular band. The dorsal interval between the setae is about equal 

 to the ventral interval between the uncini. The first achaetous seg- 

 ment at the posterior end bears a pair of perfectly normal tori, but no 

 setae or uncini. 



.The setae are often imperfect and their distribution is worked out 

 only incompletely. Anterior segments have them all slightly curved,, 

 delicate and narrowly winged, with very slender, tapering tips. They 

 occur in two series, one of finer, the other of coarser setae. Farther back 

 these two kinds become further differentiated. Both become longer 

 and the slender ones provided with short basal wings, beyond which is 

 a delicate capillary tip doubly fringed with strongly divergent, very- 

 fine hairs. 



All uncini are yellow and have the stems longitudinally striated.. 

 Those of somites II to IV, in which the number is small, have the form 

 shown in fig. 33. The stems are slender, slightly curved, regularly 

 enlarged, but with no distinct nodulus, then slightly constricted to a 

 neck, bearing a scarcely enlarged head (fig. 34), with a simple, tapering 

 unhooked beak, a small crest of three minute teeth and apparently no 

 guards. These uncini increase regularly to the dorsalmost, which 

 16 



