STYLABIOIDES PLUMOSA. 91 



Lima and mussels in the West Voe of Scalloway, Shetland. At Lochmaddy it occurs under 

 stones near low-water mark. Fine examples come from Bressay Sound. Stomach of the 

 cod and haddock, St. Andrews Bay (E. Mcintosh). Montrose Bay (Dr. Howden); Firth of 

 Forth (Leslie and Herdman) ; Plymouth (Allen) ; Dublin Bay and Clare Island (Southern). 



Abroad it ranges to Norway (H. Pathke, A. M. Norman) ; Finmark (A. M. Norman) ; 

 Atlantic coast, U.S.A. (Verrill). 



Generally distributed in the Northern seas and extending to Greenland and the 

 American shores. 



Anterior end. — The prostomium appears to be entirely hidden in the adult. Above 

 the papillose opening of the mouth are two large crenated palpi which superiorly have 

 a rose-pink lustre, probably from the iridescence of the cuticle. The frills occur on the 

 edges of a deep groove which lies on their ventral surface. Each palpus appears to have 

 a greenish central vessel, which is much paler than the branchial trunk, and when they 

 emerge they appear to be slightly folded as well as contracted. Above the palpi are the 

 grass-green branchiae, which are eight or ten in number, each with an afferent and an 

 efferent vessel, and having external circular and internal longitudinal muscular fibres 

 with hypoderm and ciliated cuticle. Both palpi and branchiae are capable of consider- 

 able elongation. In an example from Montrose Bay, forwarded long ago by the late 

 Dr. Howden, one of the left branchiae (Plate XCVI, fig. 1 a) showed a small spur near 

 the tip, thus forming a bifid organ. As this process arose from a slight hollow in the 

 outline of the branchia it may have sprung from the site of an injury. 



Body reaching 5 in. or more in length, convex on both surfaces, though having a 

 tendency to ventral flattening anteriorly and more especially posteriorly. Its calibre 

 varies according to circumstances, but it is generally somewhat larger anteriorly and 

 tapers gently to a blunt tail posteriorly. Most of the well-preserved spirit-specimens 

 show an enlargement in the anterior third and an abrupt diminution at the snout. The 

 segments range from sixty to seventy-nine, the larger examples having more segments than 

 the smaller, and they have only a single ring. The whole surface, with the exception of 

 the grooves indicating the segments, is rugose with papillae, which are elongated on the 

 dorsum and longest anteriorly, the ventral surface being distinguished by its shorter 

 papillae. These processes have externally a sheath of thickened epiderm, densest at the 

 tip, beneath which is a pale extension of the skin composed of long, tough, pale fibres 

 interwoven in all directions, which can be withdrawn from the former like a finger from 

 a glove in slightly softened specimens. They are thus studded over the skin as structures 

 shaped like nine-pins and have a central axis communicating with the hypoderm of the 

 body-wall (Plate XCV, figs. 11 — 11 b). Beneath is another layer (muscular) less tough. 



In more or less perfect examples the posterior end is slightly tapered to a blunt cone 

 with the anus toward the centre, but many examples bear evidence of reproduction of this 

 region, the vent being surrounded by a margin, and the papillae of the surface forming a 

 ring beyond it. When rupture occurs considerably in front of the anus the truncated end 

 soon cicatrises, the papillae of the surface being studded round the new anus in the centre, 

 and at first on a very blunt cone. The dorsal bristles bend toward each other, whilst the 

 hooks project boldly backward from the base of the cone. In such specimens the dorsal 

 surface is deeply grooved for some distance in front of the cicatrised end. In what 



