196 POLYCIRRUS AURANTIACITS. 



northern variety from the Hebrides and Shetland the glandular thickening at each 

 bristle-tuft is in some developed ventrally (in the preparations), so that four rows of 

 scutes appear to be present. The ventral surface is often thrown into prominent 

 transverse ruga3, which do not correspond with the processes for the long hooks. 



The body is dull yellow and semitranslucent, the intestine being visible as an 

 orange canal. Anteriorly the ventral scutes are pale, the uncinigerous processes are 

 pale yellow, the lateral glandular belt deep yellow. 



The pale golden bristles slope outward and backward from setigerous processes 

 of considerable length anteriorly, and which are bifid dorsally, the longer process being 

 posterior, and the margin curves inward ventrally. The setigerous processes become 

 smaller in their progress posteriorly, and cease before reaching the tail, the process itself 

 showing only the longer posterior papilla, the shorter being indistinguishable. The 

 number of the setigerous processes seems to be variable, ranging from thirty-five to sixty, 

 and, whilst the anterior are conspicuous, the posterior are not easily observed. The 

 bristles (Plate OXXVII, fig. 1) are in two groups, a longer and a shorter. They 

 are widest at the pale base, and gradually diminish distally, where they taper to a fine 

 point, which is curved. The longer and stronger bristles are dorsal, the shorter and 

 less robust ventral. The shorter forms are much more slender, their tapering tips alone 

 projecting beyond the surface. A simple bristle with a faintly serrated edge is figured in 

 Plate CXXVIT, fig. 1 a. In some of the stronger traces of wings are just visible. 



The uncinigerous processes commence on the ninth setigerous segment as a low 

 elevation with a short row of hooks, which in outline differ from the typical forms in the 

 middle of the body, in so far as the base is shorter and proportionally thicker, and a 

 considerable elevation occurs on the anterior outline beneath the main fang. The typical 

 forms (Plate CXXVII, fig. 1 b) have an elongated base slightly turned up at the prow, a 

 posterior outline deeply indented above the basal process, an anterior outline with a slight 

 projection below the chief fang, and a somewhat convex inferior (basal) outline. The 

 main fang is proportionally large in comparison with the neck, and the tooth above it is 

 of moderate size. A feature of these hooks is that whilst in lateral view the prow is 

 narrowed toward the point, in a view from above the end of the prow is flattened and 

 chisel-shaped. The uncinigerous processes, which are somewhat prominent posteriorly, 

 continue to the end. The row of hooks is on the anterior face of the tip (Plate CXXVII, 

 fig. lc). In the large northern variety from Shetland and the Hebrides the base of the 

 hook is somewhat thicker posteriorly. 



Habits. — Two occasionally thrust their bodies and tails into a fragment of the tube of 

 a Serpula, the anterior region and tentacles being free at the opposite end. When lifted 

 or irritated and often when put in spirit it breaks its body about the ninth bristled 

 segment, that is, behind the anterior glandular scutes, and in sea-water it pulls this 

 fragment actively about by aid of its tentacles. As Grube pointed out, it is brightly 

 phosphorescent, and by simply blowing on the water in the shallow vessel containing it 

 phosphorescent streaks appear on all the tentacles, and the corner of the vessel is so 

 illuminated that its edge can be seen. On touching a Zetlandic example brilliant bluish 

 phosphorescence gleams on every one of the tangled tentacles — spreading in a stellate 

 manner around. 



