NEREIS PELAGICA. 267 



arising from the dorsal edge. Two white longitudinal dorsal bands. Com- 

 mensal of hermit crab. Length 4 — 9 ins. 



3. Transversely elongated as well as conical paragnathi. 



Nereis cultrifera, Grube. Paragnathi conspicuous, VI transversely elongated, 

 and the basal ventral in two regular rows. 6 — 12 inches in length. 



Nereis (Stratonice) Marionii, And. & Edw. Paragnathi small, VI transversely 

 elongated at the base, pointed distally. Considerable dorsal elevation 

 commences at thirtieth foot and increases posteriorly to a long lobe with the 

 cirrus at its extremity. Length 3 — 4 ins. 



4. Paragnathi only present on the basal region of the proboscis in extrusion, or 



absent. 

 Nereis (Eunereis) longissima, Johnston. Paragnathi VI present in some. 

 Maxillary and basal regions of proboscis mapped into areas by grooves. 

 Cirri short. Length, a foot or more. 



Genus LX. — Nereis, Linnseus, 1731. (Char, emend.) 



Cephalic lobe somewhat rectangular at the base, on which the four eyes are 

 situated, whilst the anterior part is narrower and bluntly conical. Two tentacles ; palpi 

 two, lobate, with a terminal process. Nuchal organs primitive, consisting of a ciliated 

 surface in direct contact with the exterior (Racovitza) . Body sublinear, convex clorsally, 

 flattened ventrally, slightly diminished in front, more distinctly tapered posteriorly, 

 where it terminates in two caudal cirri below the vent. The first segment bears only 

 four tentacular cirri. Feet subequal throughout, sometimes foliaceous, with spines and 

 falcate bristles. Third and all succeeding feet biramous. Superior division of the foot 

 bifid, the spine not reaching the surface, and the bristles issuing from the base of the 

 fork. Proboscis armed with right and left maxilla3, strongly denticulated, and horny 

 dentiform processes (paragnathi) variously arranged, provided with powerful muscles, and 

 protrusible. (Esophagus with a pair of glands ; stomach simple and intestine straight. 



1. Nereis pelagica, Linndeus, 1756. Plate LII, figs. 1 and 2; Plate LX, figs 6 and 6 a — 

 head; Plate LXXI, figs. 7-7 i— feet; Plate LXXX, figs. 25-25 b— bristles. 



Specific Characters. — Head having a triangular anterior and a rectangular posterior 

 region with four black eyes of considerable size; the pairs wide apart and obliquely 

 situated. Tentacles and tentacular cirri of moderate length and typical. Body firm 

 and rounded, with a peristomial segment about twice the breadth of the succeeding; 

 segments sixty to eighty. Colour iridescent greenish-brown, fawn, reddish-brown, or 

 yellowish-brown, the central dorsal vessel forming a thin red line except at the moment 

 of contraction. Opposite each foot are yellowish-white grains, and often the sides and 

 feet generally present a greenish or olivaceous tint. Under surface paler, iridescent. 

 Anus often marked by a whitish opacity. The feet anteriorly are somewhat blunt and 

 bulbous at the tip. The first foot has three lobes, a dorsal, a ventral, and an intermediate 

 setigerous process which bears both homogomph and heterogomph bristles. The feet vary 



