ON A NEW SPECIES OF DEEP-SEA POLYCH/ETA. 



25 



Structural Characters of the Species. 



Color. — In specimens preserved in formalin, the dorsal surface is 

 reddish brown, fading laterally into pale-white in the middle of the para- 

 podium. Both the anterior and the posterior aspects of the latter are 

 colorless. The dorsal side of a few anteriormost body-segments is 

 entirely covered over by the elytra. Posteriorly from about the 50th 

 segment the color of the dorsum becomes gradually lighter. The 

 lines of demarcation between the segments, especially those in the 

 anterior part of the body, are inconspicuous, on account of the presence 

 of other transverse striations which might easily be mistaken for them. 



The ventral surface is pale brownish. In the median line of this 

 side there runs a pale longitudinal band marking the course of the 

 ventral nerve chain. The band runs keeping up an uniform breadth 

 nearly throughout ; only it shows a constriction at each intersegmental 

 position. Moreover, it is somewhat broadened at the anterior part 

 before it abruptly ends just behind the mouth. 



The cepJialic lobe (Pl. I., fig. 2.) is not well distinguishable from 

 the comparatively large ommatopJiores (p.), which are directed anteriorly 

 and slightly laterally. Both the cephalic lobe and the ommatophores 

 are of a brownish black color. The tip of each ommatophore shows a 

 whitish round area which gives an appearance of a lens. The unpaired 

 median tcntaculwn {int.) is small, being only about one-third the length 

 of the head ; it arises close to the posterior boundary of the latter. 

 The groove between the head and either eye is traceable nearly half 

 way down from the anterior to the posterior border of the head. Also 

 a short median groove, arising from the anterior border, may be seen 

 on the dorsal surface of the head. The paired tentacula (j>t.) arise 

 from the anterior margin of the head. They are nearly black in color 

 except the whitish boss at the end of each. A pair of snbtentacul a 

 {st.) arise from the ventral surface of the head, and are anteriorly 

 prolonged beyond the front end of this about as much as it is long 

 Their color is brownish black at base, gradually fading into light bro w 



