46 NOTOPHYLLUM FOLIOSUM. 



laminarian region, on oyster-shells and similar ground (Gravier). Genetyllis and Phyllodoce 

 Paretti and other forms, however, range to deep water — Genetyllis ocidata of the 

 ' Challenger ' coming from a depth of 500 fathoms. At the time of reproduction some 

 become pelagic, and develop a dorsal series of long natatory bristles. 



The colours of those from the deep sea are of the same character as those from 

 shallow water. 



Genus XXX. — jNTotophyllum, Oersted, 1843. Char, emend. 



Body linear, tapered gently at each extremity, dorsum convex, ventral surface 

 grooved and flattened. Two considerable eyes. Tentacles five, four anterior and one 

 median. Tentacular cirri on two segments (Grube), four on each side, two shorter in 

 front and two longer posteriorly. Superior division of the foot little differentiated, yet 

 with a spine and a few simple bristles, and supporting a large irregularly reniform 

 dorsal cirrus, the series being imbricate and almost covering the back and the feet. The 

 inferior division has a much smaller vertical and somewhat reniform lamella, and a spine 

 with many bristles, the shafts of which are curved distally and end in a dilated region 

 having a series of spikes guarding the base of the long sabre-shaped distal blade, which 

 has its edge very minutely serrated. The ventral border of the foot has a prominent 

 process or mamilla, to which the inner edge of the lamellar cirrus is attached. Ganglia of 

 the ventral cords large, resting on the sheath, with the circular muscular fibres externally, 

 the oblique passing down on each side. In the interganglionic areas the insertions of the 

 oblique muscles are nearer each other. The dorsal longitudinal muscles are completely 

 separated and very broad. The ventral longitudinal muscles are compact. 



Notophyllum is said by Gravier 1 to have a small nerve-cord running above the two 

 great cords. The sections of the British forms did not show this clearly, and thus 

 differed from those of Nereis diversicolor, in which a third interganglionic cord with 

 a neural canal is present. 



1. Xotophyllum foliosum, Sars, 1835. Plate XLV, fig. 1; Plate LXVII, fig. 5— foot ; 



Plate LXXVII, fig. 21— bristles. 



Specific Characters.— -Head forming a rounded cone, with two considerable eyes, 

 occasionally with cuticular lenses. A ciliated flap or lappet on each side of the head 

 posteriorly. Tentacles, five ; two occur on each side of the snout, are flattened, and 

 somewhat pointed and shorter than the median. Two shorter and two longer tentacular 

 cirri on each side. All these processes, as well as the head, are greenish-yellow with 

 darker grains. Body linear, gently tapered anteriorly, convex dorsally, flattened ventrally, 

 with a rectal papilla in the centre posteriorly. Proboscis smooth. Dorsal lobe of the 

 foot directed upward and prolonged inward as a narrow process from which the great 

 and more or less horizontal and irregularly reniform dorsal lamella (cirrus) springs. A 

 slender spine and a few tapering smooth bristles occur towards the ventral edge of the 



1 < Bullet. Sc. Fr. Belg.,' 29, p. 331, pi. xix, f. 19. 



