AMPHITRITE AFFINIS. 113 



Habitat— Dredged in the "Porcupine" Expedition of 1869, at 808 fathoms at 

 Station 11, off the Irish coast, in sticky mud. Dredged by the "Knight Errant" 

 at Station 11, 28th August, 1880, in 535 fathoms; Clew Bay (Southern). 



Abroad it has been found in Spitzbergen (Malmgren) ; Norway (Danielssen, Wolle- 

 bask) ; Iceland and Siberia. 



The cephalic region presents a broad horse-shoe fold over the mouth, continuous at 

 its outer and inferior edge, with the larger collar which bounds the tentacular area 

 posteriorly. A deep groove, wide in the middle and tapered at each side, is thus formed. 

 Below the mouth is a short fold bounded by the first-mentioned horse-shoe arch at 

 each side, and ventral to this a broader band or lip. 



The body is typical, so far as it goes, is rounded dorsally, whilst ventrally are twelve 

 distinct shields and several rudimentary ones posteriorly. Behind the mouth is a 

 transverse shield which dorsally joins the smooth region behind the collar. Two 

 segments with ventral shields follow, the dorsal edge of the first passing to the base of 

 the first branchia, whilst the dorsal edge of the second falls short of its branchia. In 

 all twelve shields are present. A still larger gap separates the first bristle-tuft of the 

 next segment from the third branchia. Behind the shields a deep groove occupies the 

 ventral median line. A ridge (marking the nerve-cord) is continued from the last ventral 

 plate or shield along the groove to the posterior end of the body. 



Marenzeller describes the colour of the body as reddish grey, brownish in front and 

 pale posteriorly. Tentacles streaked and punctated with brown. In the examples from 

 the " Porcupine " brownish pigment still remained anteriorly at the cephalic folds and 

 between the ventral shields. 



The branchias are three in number, proportionally small and with short and rather 

 thick terminal divisions. The first (Plate CXX, fig. 10) has a short stem which splits ; 

 each branch consists of a few short, slightly curled filaments, some with bifid tips. The 

 second is a little less, and the third is again smaller. Both sides are alike, and on the 

 whole the organs seem to be somewhat shorter than in A. cirrata. 



There are seventeen pairs of bristle-tufts, the first commencing opposite the third 

 branchia. The bristles (Plate CXXV, fig. 6) are pale golden, the shaft being deeply 

 inserted in the tissues, only a short free portion occurring below the wings, which are 

 narrow and soon cease, the translucent tip beyond being flattened like a long knife-blade, 

 boldly serrated at the edge, and tapered to a very long hair-like tip. One or two shorter 

 forms occur amongst the others, but apparently no regular series as in other genera, and 

 some may be developing long bristles. In these little of the winged region projects 

 beyond the surface, and the flattened blade is occasionally split into spikes. Amongst 

 the bristles are long curved forms with narrow wings (Plate CXXV, fig. 6') and 

 finely tapered tips. The bristles issue from an elevation at the dorsal edge of the ridge 

 for the hooks, and they form a vertical series in each tuft. Moreover, six small papilla 

 (third to ninth segments) occur immediately beneath them, situated at the posterior 

 border of the ridge for the hooks. 



The hooks (Plate CXXV, figs. 6 a and 6 a'), when fully developed, form a double row, 

 the large fang facing that of the opposite hook. The base is comparatively small and 

 the crown and neck large (Plate CXXVI, fig. 2 b). The crown presents in lateral 



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