222 
THE VOYAGE OE H.M.S. CHALLENGER. 
Nereis longisetis, n. sp, (PL XXXV. fig. 4 ; PI. XVIa. figs. 12, 13, 19). 
Habitat. — Trawled at Station VI. (off the Strait of Gibraltar), January 30, 1873 ; lat. 
36° 23' N., long. 11° 18' W.; depth, 1525 fatlioms ; bottom temperature 36°'0, surface 
temperature 58°'0 ; sea-bottom, Globigerina ooze. 
Head longer than broad ; tentacles about half the length. Anterior eyes dorsal in 
position, much larger than the posterior, and furnished with lenses. Paragnathi few 
and scattered. Maxillae have about five teeth below the fang. Anterior feet with 
pointed lobes ; the latter becoming much longer posteriorly. Bristles very large and long ; 
the majority in the groups have long dagger-shaped tips, but at the ventral edge these 
are much abbreviated. A few with shorter tips, intermediate in structure between the 
long dagger-shaped and falcate bristles. 
A fragmentary and injured example, measuring about 10 mm., and having a total 
breadth (across the bristles) of nearly 3 mm. 
The head (PI. XXXV. fig. 4) is longer than broad, with tw'O very large and somewhat 
ovoid anterior eyes, apparently furnished with indistinct lenses ; and two much smaller 
eyes behind. The latter have no trace of lenses, and the injured condition of the anterior 
pair renders their description doubtful. The tentacles are short and subulate, being about 
half the antero-posterior diameter of the head. The tentacular cirri are either injured or 
absent. The large size of the anterior eyes, tlieir dorsal position, and the disproportion 
between them and the- posterior pair, are the chief characteristics of the head. 
The buccal segment is broader than the succeeding, and the first three bristled 
segments are broader than those which immediately follow. Unfortunately the proboscis 
is injured, and all that can be said about the paragnathi is that they are few and scattered. 
The maxillary teeth are about five in number. 
In most of the feet after the anterior third the second lobe is directed forward, a 
feature which gives tlie long posterior feet a resemblance to those in Glycera. 
The dorsal cirrus of the tenth foot is slender and filiform, and somewhat shorter than 
the superior lobe. The second lobe is very large, broad at the base, and conical toward 
the tip, which extends much beyond the first. The setigerous (inferior) division is short. 
The ventral lobe is broadly conical, and points outward and downward. The ventral 
cirrus seems to be short. The shafts of the superior bristles (PI. XVIa. fig. 12) are long, 
and the tips are of moderate length, and slightly spinous. The setose, inferior bristles 
are similar to the foregoing, while those corresponding to the falcate have a long, slightly 
bent, dagger-shaped process, as in Ilesione ; indeed such tips are the longest yet observed 
in the Nereidse. 
At the twenty-seventh foot the chief change is the great elongation of the second 
lobe, the spine passing out to a papilla which projects further than the superior lobe. 
Beyond is a pointed process nearly as large as the entire superior region, and it is this 
