celetopterim;. 115 



having the two kinds of papillae, viz. long urn-shaped, and clavate forms on long stalks 

 (Plate XCVI, fig. 11). It is at once distinguished, however, by its deep brick-red colour, 

 the two long palpi being pale, whilst the branchiae are of a very deep red. In comparing 

 the urn-shaped papillae of this form with those of F. affinis the only difference appears to 

 be that in F. buslcii the central granular (hypodermic) axis is more distinct at the tip, a 

 clear granule generally occurring in the centre, whereas in F. affinis the whole tip is more 

 slender and the axial substance less evident. The clavate papillae again appear to be 

 proportionally smaller and the stalk thicker and shorter. Minute sand-grains and other 

 debris are attached to the gelatinous investment as in the common species. 



The arrangement of the parts at the mouth appears to be similar to those of F. affinis, 

 but the branchiae have a very deep red colour, thus showing that the circulatory fluid has 

 the same tint. The palpi on the other hand are pale. 



The frontal bristles (Plate Oil, fig. 3) are more translucent and slender than in 

 specimens of F. affinis of the same size, and the articulations are longer throughout, as 

 indicated in fig. 8 a, Plate CIV, an ordinary bristle being represented in fig. 8. 



They have various parasitic growths and are accompanied by the urn-shaped 

 papillae. 



The hooks (Plate CII, figs. 3 a and 3 b) have a more slender shaft with longer 

 articulations, and the breadth and length of the terminal claw are greater whilst the 

 curvature of the claw and its relation to the shaft differ. When the hook or shaft are 

 broken it separates obliquely at a, a little above the articulation, leaving the short process 

 through which the dotted line passes. 



Family XX. — Ch^etopterid^. 1 



Ch^topteriens, Audouin and Edwards, 1834 



The head is broad, flattened, but not distinctly separated from the adjoining region. 

 It bears (from the peristomium) two long, grooved tentacles with an eye at the outer base 

 of each. The mouth is large. 



Body composed of three regions, an anterior usually of nine bristled segments, some 

 of the bristles being powerful, a middle region of five segments peculiarly modified, and 

 a posterior region of variable length, each segment bearing a large dorsal lobe enclosing 

 acerate bristles and a ventral enlargement with hooks. The fourth setigerous segment 

 has bristles which are specially powerful. Nerve-cords hypodermic in position, wide apart. 

 Tubes of shells, stones, and other fragments lined by a tough parchment-like secretion and 

 comparatively large. 



The body-wall, anteriorly (Fig. Ill), in Chxtopterus variopedatus,a,8 Claparede pointed 

 out, is complex, for laterally it is produced into two prominent wings (al.) having pro- 

 portionally large bristles, and from its flattened condition the muscular system under- 

 goes much modification. Externally is a thin ciliated cuticle covering the largely 

 developed hypoderm (hyp.) with its spherical or pyriform glands which rest on a 



1 XatTt], bristle, and irrepov, wing. 



