330 NEREIS (ALITTA) VIRENS. 



The Leptonereis vasculosa of Griard 2 appears to approach this form closely, and is 

 also characterized by the feeble armature of the proboscis. 



8. Nereis (Alitta) virens, Sars, 1835. Plate LIII; Plate L, figs. 12, 13, and 16— larval 

 and post-larval; Plate LXI, figs. 2 and 2 a — head, and figs. 3-5 — other parts; 

 Plate LXXIII, figs. 2-2 6— feet ; Plate LXXXI, fig. 7— bristles. 



Specific Characters. — Head typical in outline, with two short tentacles anteriorly. 

 Eyes four, arranged in a trapezoid, toward the posterior part of the head, the anterior 

 pair wider apart, a line from each posterior eye sloping inward and backward to the 

 nuchal bridge. The longest tentacular cirrus is the dorsal of the second pair. Colour 

 bluish-purple, and in the preparations often presenting a longitudinal median groove, the 

 ridge on each side running forward to the frontal tentacle. Body from 1 — 3 feet in 

 length, and If inches in breadth across the feet in a large specimen, slightly tapered 

 anteriorly, diminishing posteriorly, and ending in an anal segment with two long cirri. 

 Peristomial segment twice the breadth of the succeeding. Dorsum of various shades of 

 iridescent bluish-purple, and the lamella of the feet are also finely tinted and iridescent ; 

 dorsal cirrus larger anteriorly than in those with foliaceous lamellae, and of a deep green. 

 Ventral surface pale iridescent pinkish, deeper posteriorly, but in some iridescent bluish, 

 with the belts at the anterior part of each segment of a deeper hue. Proboscis in 

 extrusion greyish-blue, somewhat lighter than the hue of the body. The maxillas have 

 six teeth. The maxillary segment dorsally has a triangular group of paragnathi with the 

 apex in front, on each side behind the jaw, sometimes forming a double row with the 

 limbs wider apart posteriorly, and two points — one in front of the other — between them. 

 Ventrally a long, rather irregular double row proceeds in the maxillary division backward 

 from each jaw, and in the middle is a transverse belt of points, or a larger group in the 

 central area, and a point or two in the lateral area on each side. The proximal segment 

 has dorsally on the eminence in front of each palpus one or two paragnathi, and between 

 them a single point. Ventrally is an irregular double row of paragnathi on the folds, 

 and a brief interval exists between them and the dorsal points. First foot has a dorsal, 

 a middle, and a ventral lobe, the setigerous process being attached to the anterior face of 

 the middle lobe. These lobes are subequal, and nearly lanceolate in outline. The dorsal 

 and ventral cirri are somewhat short, in neither case reaching the tip of the adjoining 

 lobe. The succeeding feet present a tendency to the increase of the dorsal lobe, so that 

 at the tenth foot it forms a large foliaceous lamella. The superior setigerous lobe has a 

 lanceolate lamella beneath it, whilst, after a gap, the inferior setigerous lobe has one above 

 it in lateral view. The dorsal lamella gradually increases until (as at the thirty-seventh 

 foot) it forms a great lanceolate leaf overlapping that behind. The middle lamella is also 

 large and foliaceous, and the cirri appear small beside it. The foot retains this structure 

 till near the tip of the tail. All the bristles have simple tapering tips, those at the 

 ventral edge of the inferior division having shorter tips of the same kind. The shafts are 

 finely camerated. 



Ehlers describes the epitokous form as having the upper lamellse of the feet much 

 1 'Ball. Sc. Fr. et Belg./ T. xxii, p. 78, 1890. 



